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Python 3.6.5 Documentation > Built-in Functions

Built-in Functions
******************

The Python interpreter has a number of functions and types built into
it that are always available. They are listed here in alphabetical
order.

+---------------------+-------------------+--------------------+------------------+----------------------+
| | | Built-in Functions | | |
+=====================+===================+====================+==================+======================+
| "abs()" | "dict()" | "help()" | "min()" | "setattr()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "all()" | "dir()" | "hex()" | "next()" | "slice()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "any()" | "divmod()" | "id()" | "object()" | "sorted()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "ascii()" | "enumerate()" | "input()" | "oct()" | "staticmethod()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "bin()" | "eval()" | "int()" | "open()" | "str()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "bool()" | "exec()" | "isinstance()" | "ord()" | "sum()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "bytearray()" | "filter()" | "issubclass()" | "pow()" | "super()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "bytes()" | "float()" | "iter()" | "print()" | "tuple()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "callable()" | "format()" | "len()" | "property()" | "type()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "chr()" | "frozenset()" | "list()" | "range()" | "vars()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "classmethod()" | "getattr()" | "locals()" | "repr()" | "zip()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "compile()" | "globals()" | "map()" | "reversed()" | "__import__()" |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "complex()" | "hasattr()" | "max()" | "round()" | |
+---------------------+-------------------+--------------------+------------------+----------------------+
| "delattr()" | "hash()" | "memoryview()" | "set()" | |
+---------------------+-------------------+--------------------+------------------+----------------------+

abs(x)

Return the absolute value of a number. The argument may be an
integer or a floating point number. If the argument is a complex
number, its magnitude is returned.

all(iterable)

Return "True" if all elements of the *iterable* are true (or if the
iterable is empty). Equivalent to:

def all(iterable):
for element in iterable:
if not element:
return False
return True

any(iterable)

Return "True" if any element of the *iterable* is true. If the
iterable is empty, return "False". Equivalent to:

def any(iterable):
for element in iterable:
if element:
return True
return False

ascii(object)

As "repr()", return a string containing a printable representation
of an object, but escape the non-ASCII characters in the string
returned by "repr()" using "\x", "\u" or "\U" escapes. This
generates a string similar to that returned by "repr()" in Python
2.

bin(x)

Convert an integer number to a binary string prefixed with “0b”.
The result is a valid Python expression. If *x* is not a Python
"int" object, it has to define an "__index__()" method that
returns an integer. Some examples:

>>> bin(3)
'0b11'
>>> bin(-10)
'-0b1010'

If prefix “0b” is desired or not, you can use either of the
following ways.

>>> format(14, '#b'), format(14, 'b')
('0b1110', '1110')
>>> f'{14:#b}', f'{14:b}'
('0b1110', '1110')

See also "format()" for more information.

class bool([x])

Return a Boolean value, i.e. one of "True" or "False". *x* is
converted using the standard truth testing procedure. If *x* is
false or omitted, this returns "False"; otherwise it returns
"True". The "bool" class is a subclass of "int" (see Numeric Types
— int, float, complex). It cannot be subclassed further. Its only
instances are "False" and "True" (see Boolean Values).

class bytearray([source[, encoding[, errors]]])

Return a new array of bytes. The "bytearray" class is a mutable
sequence of integers in the range 0 <= x < 256. It has most of the
usual methods of mutable sequences, described in Mutable Sequence
Types, as well as most methods that the "bytes" type has, see Bytes
and Bytearray Operations.

The optional *source* parameter can be used to initialize the array
in a few different ways:

* If it is a *string*, you must also give the *encoding* (and
optionally, *errors*) parameters; "bytearray()" then converts the
string to bytes using "str.encode()".

* If it is an *integer*, the array will have that size and will
be initialized with null bytes.

* If it is an object conforming to the *buffer* interface, a
read- only buffer of the object will be used to initialize the
bytes array.

* If it is an *iterable*, it must be an iterable of integers in
the range "0 <= x < 256", which are used as the initial contents
of the array.

Without an argument, an array of size 0 is created.

See also Binary Sequence Types — bytes, bytearray, memoryview and
Bytearray Objects.

class bytes([source[, encoding[, errors]]])

Return a new “bytes” object, which is an immutable sequence of
integers in the range "0 <= x < 256". "bytes" is an immutable
version of "bytearray" – it has the same non-mutating methods and
the same indexing and slicing behavior.

Accordingly, constructor arguments are interpreted as for
"bytearray()".

Bytes objects can also be created with literals, see String and
Bytes literals.

See also Binary Sequence Types — bytes, bytearray, memoryview,
Bytes Objects, and Bytes and Bytearray Operations.

callable(object)

Return "True" if the *object* argument appears callable, "False" if
not. If this returns true, it is still possible that a call fails,
but if it is false, calling *object* will never succeed. Note that
classes are callable (calling a class returns a new instance);
instances are callable if their class has a "__call__()" method.

New in version 3.2: This function was first removed in Python 3.0
and then brought back in Python 3.2.

chr(i)

Return the string representing a character whose Unicode code point
is the integer *i*. For example, "chr(97)" returns the string
"'a'", while "chr(8364)" returns the string "'€'". This is the
inverse of "ord()".

The valid range for the argument is from 0 through 1,114,111
(0x10FFFF in base 16). "ValueError" will be raised if *i* is
outside that range.

@classmethod

Transform a method into a class method.

A class method receives the class as implicit first argument, just
like an instance method receives the instance. To declare a class
method, use this idiom:

class C:
@classmethod
def f(cls, arg1, arg2, ...): ...

The "@classmethod" form is a function *decorator* – see the
description of function definitions in Function definitions for
details.

It can be called either on the class (such as "C.f()") or on an
instance (such as "C().f()"). The instance is ignored except for
its class. If a class method is called for a derived class, the
derived class object is passed as the implied first argument.

Class methods are different than C++ or Java static methods. If you
want those, see "staticmethod()" in this section.

For more information on class methods, consult the documentation on
the standard type hierarchy in The standard type hierarchy.

compile(source, filename, mode, flags=0, dont_inherit=False, optimize=-1)

Compile the *source* into a code or AST object. Code objects can
be executed by "exec()" or "eval()". *source* can either be a
normal string, a byte string, or an AST object. Refer to the "ast"
module documentation for information on how to work with AST
objects.

The *filename* argument should give the file from which the code
was read; pass some recognizable value if it wasn’t read from a
file ("'<string>'" is commonly used).

The *mode* argument specifies what kind of code must be compiled;
it can be "'exec'" if *source* consists of a sequence of
statements, "'eval'" if it consists of a single expression, or
"'single'" if it consists of a single interactive statement (in the
latter case, expression statements that evaluate to something other
than "None" will be printed).

The optional arguments *flags* and *dont_inherit* control which
future statements (see **PEP 236**) affect the compilation of
*source*. If neither is present (or both are zero) the code is
compiled with those future statements that are in effect in the
code that is calling "compile()". If the *flags* argument is given
and *dont_inherit* is not (or is zero) then the future statements
specified by the *flags* argument are used in addition to those
that would be used anyway. If *dont_inherit* is a non-zero integer
then the *flags* argument is it – the future statements in effect
around the call to compile are ignored.

Future statements are specified by bits which can be bitwise ORed
together to specify multiple statements. The bitfield required to
specify a given feature can be found as the "compiler_flag"
attribute on the "_Feature" instance in the "__future__" module.

The argument *optimize* specifies the optimization level of the
compiler; the default value of "-1" selects the optimization level
of the interpreter as given by "-O" options. Explicit levels are
"0" (no optimization; "__debug__" is true), "1" (asserts are
removed, "__debug__" is false) or "2" (docstrings are removed too).

This function raises "SyntaxError" if the compiled source is
invalid, and "ValueError" if the source contains null bytes.

If you want to parse Python code into its AST representation, see
"ast.parse()".

Note: When compiling a string with multi-line code in "'single'"
or "'eval'" mode, input must be terminated by at least one
newline character. This is to facilitate detection of incomplete
and complete statements in the "code" module.

Warning: It is possible to crash the Python interpreter with a
sufficiently large/complex string when compiling to an AST object
due to stack depth limitations in Python’s AST compiler.

Changed in version 3.2: Allowed use of Windows and Mac newlines.
Also input in "'exec'" mode does not have to end in a newline
anymore. Added the *optimize* parameter.

Changed in version 3.5: Previously, "TypeError" was raised when
null bytes were encountered in *source*.

class complex([real[, imag]])

Return a complex number with the value *real* + *imag**1j or
convert a string or number to a complex number. If the first
parameter is a string, it will be interpreted as a complex number
and the function must be called without a second parameter. The
second parameter can never be a string. Each argument may be any
numeric type (including complex). If *imag* is omitted, it
defaults to zero and the constructor serves as a numeric conversion
like "int" and "float". If both arguments are omitted, returns
"0j".

Note: When converting from a string, the string must not contain
whitespace around the central "+" or "-" operator. For example,
"complex('1+2j')" is fine, but "complex('1 + 2j')" raises
"ValueError".

The complex type is described in Numeric Types — int, float,
complex.

Changed in version 3.6: Grouping digits with underscores as in code
literals is allowed.

delattr(object, name)

This is a relative of "setattr()". The arguments are an object and
a string. The string must be the name of one of the object’s
attributes. The function deletes the named attribute, provided the
object allows it. For example, "delattr(x, 'foobar')" is
equivalent to "del x.foobar".

class dict(**kwarg)
class dict(mapping, **kwarg)
class dict(iterable, **kwarg)

Create a new dictionary. The "dict" object is the dictionary
class. See "dict" and Mapping Types — dict for documentation about
this class.

For other containers see the built-in "list", "set", and "tuple"
classes, as well as the "collections" module.

dir([object])

Without arguments, return the list of names in the current local
scope. With an argument, attempt to return a list of valid
attributes for that object.

If the object has a method named "__dir__()", this method will be
called and must return the list of attributes. This allows objects
that implement a custom "__getattr__()" or "__getattribute__()"
function to customize the way "dir()" reports their attributes.

If the object does not provide "__dir__()", the function tries its
best to gather information from the object’s "__dict__" attribute,
if defined, and from its type object. The resulting list is not
necessarily complete, and may be inaccurate when the object has a
custom "__getattr__()".

The default "dir()" mechanism behaves differently with different
types of objects, as it attempts to produce the most relevant,
rather than complete, information:

* If the object is a module object, the list contains the names
of the module’s attributes.

* If the object is a type or class object, the list contains the
names of its attributes, and recursively of the attributes of its
bases.

* Otherwise, the list contains the object’s attributes’ names,
the names of its class’s attributes, and recursively of the
attributes of its class’s base classes.

The resulting list is sorted alphabetically. For example:

>>> import struct
>>> dir() # show the names in the module namespace
['__builtins__', '__name__', 'struct']
>>> dir(struct) # show the names in the struct module # doctest: +SKIP
['Struct', '__all__', '__builtins__', '__cached__', '__doc__', '__file__',
'__initializing__', '__loader__', '__name__', '__package__',
'_clearcache', 'calcsize', 'error', 'pack', 'pack_into',
'unpack', 'unpack_from']
>>> class Shape:
... def __dir__(self):
... return ['area', 'perimeter', 'location']
>>> s = Shape()
>>> dir(s)
['area', 'location', 'perimeter']

Note: Because "dir()" is supplied primarily as a convenience for
use at an interactive prompt, it tries to supply an interesting
set of names more than it tries to supply a rigorously or
consistently defined set of names, and its detailed behavior may
change across releases. For example, metaclass attributes are
not in the result list when the argument is a class.

divmod(a, b)

Take two (non complex) numbers as arguments and return a pair of
numbers consisting of their quotient and remainder when using
integer division. With mixed operand types, the rules for binary
arithmetic operators apply. For integers, the result is the same
as "(a // b, a % b)". For floating point numbers the result is "(q,
a % b)", where *q* is usually "math.floor(a / b)" but may be 1 less
than that. In any case "q * b + a % b" is very close to *a*, if "a
% b" is non-zero it has the same sign as *b*, and "0 <= abs(a % b)
< abs(b)".

enumerate(iterable, start=0)

Return an enumerate object. *iterable* must be a sequence, an
*iterator*, or some other object which supports iteration. The
"__next__()" method of the iterator returned by "enumerate()"
returns a tuple containing a count (from *start* which defaults to
0) and the values obtained from iterating over *iterable*.

>>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
>>> list(enumerate(seasons))
[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
>>> list(enumerate(seasons, start=1))
[(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]

Equivalent to:

def enumerate(sequence, start=0):
n = start
for elem in sequence:
yield n, elem
n += 1

eval(expression, globals=None, locals=None)

The arguments are a string and optional globals and locals. If
provided, *globals* must be a dictionary. If provided, *locals*
can be any mapping object.

The *expression* argument is parsed and evaluated as a Python
expression (technically speaking, a condition list) using the
*globals* and *locals* dictionaries as global and local namespace.
If the *globals* dictionary is present and lacks ‘__builtins__’,
the current globals are copied into *globals* before *expression*
is parsed. This means that *expression* normally has full access
to the standard "builtins" module and restricted environments are
propagated. If the *locals* dictionary is omitted it defaults to
the *globals* dictionary. If both dictionaries are omitted, the
expression is executed in the environment where "eval()" is called.
The return value is the result of the evaluated expression. Syntax
errors are reported as exceptions. Example:

>>> x = 1
>>> eval('x+1')
2

This function can also be used to execute arbitrary code objects
(such as those created by "compile()"). In this case pass a code
object instead of a string. If the code object has been compiled
with "'exec'" as the *mode* argument, "eval()"’s return value will
be "None".

Hints: dynamic execution of statements is supported by the "exec()"
function. The "globals()" and "locals()" functions returns the
current global and local dictionary, respectively, which may be
useful to pass around for use by "eval()" or "exec()".

See "ast.literal_eval()" for a function that can safely evaluate
strings with expressions containing only literals.

exec(object[, globals[, locals]])

This function supports dynamic execution of Python code. *object*
must be either a string or a code object. If it is a string, the
string is parsed as a suite of Python statements which is then
executed (unless a syntax error occurs). [1] If it is a code
object, it is simply executed. In all cases, the code that’s
executed is expected to be valid as file input (see the section
“File input” in the Reference Manual). Be aware that the "return"
and "yield" statements may not be used outside of function
definitions even within the context of code passed to the "exec()"
function. The return value is "None".

In all cases, if the optional parts are omitted, the code is
executed in the current scope. If only *globals* is provided, it
must be a dictionary, which will be used for both the global and
the local variables. If *globals* and *locals* are given, they are
used for the global and local variables, respectively. If
provided, *locals* can be any mapping object. Remember that at
module level, globals and locals are the same dictionary. If exec
gets two separate objects as *globals* and *locals*, the code will
be executed as if it were embedded in a class definition.

If the *globals* dictionary does not contain a value for the key
"__builtins__", a reference to the dictionary of the built-in
module "builtins" is inserted under that key. That way you can
control what builtins are available to the executed code by
inserting your own "__builtins__" dictionary into *globals* before
passing it to "exec()".

Note: The built-in functions "globals()" and "locals()" return
the current global and local dictionary, respectively, which may
be useful to pass around for use as the second and third argument
to "exec()".

Note: The default *locals* act as described for function
"locals()" below: modifications to the default *locals*
dictionary should not be attempted. Pass an explicit *locals*
dictionary if you need to see effects of the code on *locals*
after function "exec()" returns.

filter(function, iterable)

Construct an iterator from those elements of *iterable* for which
*function* returns true. *iterable* may be either a sequence, a
container which supports iteration, or an iterator. If *function*
is "None", the identity function is assumed, that is, all elements
of *iterable* that are false are removed.

Note that "filter(function, iterable)" is equivalent to the
generator expression "(item for item in iterable if
function(item))" if function is not "None" and "(item for item in
iterable if item)" if function is "None".

See "itertools.filterfalse()" for the complementary function that
returns elements of *iterable* for which *function* returns false.

class float([x])

Return a floating point number constructed from a number or string
*x*.

If the argument is a string, it should contain a decimal number,
optionally preceded by a sign, and optionally embedded in
whitespace. The optional sign may be "'+'" or "'-'"; a "'+'" sign
has no effect on the value produced. The argument may also be a
string representing a NaN (not-a-number), or a positive or negative
infinity. More precisely, the input must conform to the following
grammar after leading and trailing whitespace characters are
removed:

sign ::= "+" | "-"
infinity ::= "Infinity" | "inf"
nan ::= "nan"
numeric_value ::= floatnumber | infinity | nan
numeric_string ::= [sign] numeric_value

Here "floatnumber" is the form of a Python floating-point literal,
described in Floating point literals. Case is not significant, so,
for example, “inf”, “Inf”, “INFINITY” and “iNfINity” are all
acceptable spellings for positive infinity.

Otherwise, if the argument is an integer or a floating point
number, a floating point number with the same value (within
Python’s floating point precision) is returned. If the argument is
outside the range of a Python float, an "OverflowError" will be
raised.

For a general Python object "x", "float(x)" delegates to
"x.__float__()".

If no argument is given, "0.0" is returned.

Examples:

>>> float('+1.23')
1.23
>>> float(' -12345\n')
-12345.0
>>> float('1e-003')
0.001
>>> float('+1E6')
1000000.0
>>> float('-Infinity')
-inf

The float type is described in Numeric Types — int, float, complex.

Changed in version 3.6: Grouping digits with underscores as in code
literals is allowed.

format(value[, format_spec])

Convert a *value* to a “formatted” representation, as controlled by
*format_spec*. The interpretation of *format_spec* will depend on
the type of the *value* argument, however there is a standard
formatting syntax that is used by most built-in types: Format
Specification Mini-Language.

The default *format_spec* is an empty string which usually gives
the same effect as calling "str(value)".

A call to "format(value, format_spec)" is translated to
"type(value).__format__(value, format_spec)" which bypasses the
instance dictionary when searching for the value’s "__format__()"
method. A "TypeError" exception is raised if the method search
reaches "object" and the *format_spec* is non-empty, or if either
the *format_spec* or the return value are not strings.

Changed in version 3.4: "object().__format__(format_spec)" raises
"TypeError" if *format_spec* is not an empty string.

class frozenset([iterable])

Return a new "frozenset" object, optionally with elements taken
from *iterable*. "frozenset" is a built-in class. See "frozenset"
and Set Types — set, frozenset for documentation about this class.

For other containers see the built-in "set", "list", "tuple", and
"dict" classes, as well as the "collections" module.

getattr(object, name[, default])

Return the value of the named attribute of *object*. *name* must
be a string. If the string is the name of one of the object’s
attributes, the result is the value of that attribute. For
example, "getattr(x, 'foobar')" is equivalent to "x.foobar". If
the named attribute does not exist, *default* is returned if
provided, otherwise "AttributeError" is raised.

globals()

Return a dictionary representing the current global symbol table.
This is always the dictionary of the current module (inside a
function or method, this is the module where it is defined, not the
module from which it is called).

hasattr(object, name)

The arguments are an object and a string. The result is "True" if
the string is the name of one of the object’s attributes, "False"
if not. (This is implemented by calling "getattr(object, name)" and
seeing whether it raises an "AttributeError" or not.)

hash(object)

Return the hash value of the object (if it has one). Hash
values are integers. They are used to quickly compare
dictionary keys during a dictionary lookup. Numeric values that
compare equal have the same hash value (even if they are of
different types, as is the case for 1 and 1.0).

Note: For objects with custom "__hash__()" methods, note that
"hash()" truncates the return value based on the bit width of the
host machine. See "__hash__()" for details.

help([object])

Invoke the built-in help system. (This function is intended for
interactive use.) If no argument is given, the interactive help
system starts on the interpreter console. If the argument is a
string, then the string is looked up as the name of a module,
function, class, method, keyword, or documentation topic, and a
help page is printed on the console. If the argument is any other
kind of object, a help page on the object is generated.

This function is added to the built-in namespace by the "site"
module.

Changed in version 3.4: Changes to "pydoc" and "inspect" mean that
the reported signatures for callables are now more comprehensive
and consistent.

hex(x)

Convert an integer number to a lowercase hexadecimal string
prefixed with “0x”. If x is not a Python "int" object, it has to
define an __index__() method that returns an integer. Some
examples:

>>> hex(255)
'0xff'
>>> hex(-42)
'-0x2a'

If you want to convert an integer number to an uppercase or lower
hexadecimal string with prefix or not, you can use either of the
following ways:

>>> '%#x' % 255, '%x' % 255, '%X' % 255
('0xff', 'ff', 'FF')
>>> format(255, '#x'), format(255, 'x'), format(255, 'X')
('0xff', 'ff', 'FF')
>>> f'{255:#x}', f'{255:x}', f'{255:X}'
('0xff', 'ff', 'FF')

See also "format()" for more information.

See also "int()" for converting a hexadecimal string to an integer
using a base of 16.

Note: To obtain a hexadecimal string representation for a float,
use the "float.hex()" method.

id(object)

Return the “identity” of an object. This is an integer which is
guaranteed to be unique and constant for this object during its
lifetime. Two objects with non-overlapping lifetimes may have the
same "id()" value.

**CPython implementation detail:** This is the address of the
object in memory.

input([prompt])

If the *prompt* argument is present, it is written to standard
output without a trailing newline. The function then reads a line
from input, converts it to a string (stripping a trailing newline),
and returns that. When EOF is read, "EOFError" is raised.
Example:

>>> s = input('--> ') # doctest: +SKIP
--> Monty Python's Flying Circus
>>> s # doctest: +SKIP
"Monty Python's Flying Circus"

If the "readline" module was loaded, then "input()" will use it to
provide elaborate line editing and history features.

class int(x=0)
class int(x, base=10)

Return an integer object constructed from a number or string *x*,
or return "0" if no arguments are given. If *x* is a number,
return "x.__int__()". If *x* defines "x.__trunc__()" but not
"x.__int__()", then return if "x.__trunc__()". For floating point
numbers, this truncates towards zero.

If *x* is not a number or if *base* is given, then *x* must be a
string, "bytes", or "bytearray" instance representing an integer
literal in radix *base*. Optionally, the literal can be preceded
by "+" or "-" (with no space in between) and surrounded by
whitespace. A base-n literal consists of the digits 0 to n-1, with
"a" to "z" (or "A" to "Z") having values 10 to 35. The default
*base* is 10. The allowed values are 0 and 2–36. Base-2, -8, and
-16 literals can be optionally prefixed with "0b"/"0B", "0o"/"0O",
or "0x"/"0X", as with integer literals in code. Base 0 means to
interpret exactly as a code literal, so that the actual base is 2,
8, 10, or 16, and so that "int('010', 0)" is not legal, while
"int('010')" is, as well as "int('010', 8)".

The integer type is described in Numeric Types — int, float,
complex.

Changed in version 3.4: If *base* is not an instance of "int" and
the *base* object has a "base.__index__" method, that method is
called to obtain an integer for the base. Previous versions used
"base.__int__" instead of "base.__index__".

Changed in version 3.6: Grouping digits with underscores as in code
literals is allowed.

isinstance(object, classinfo)

Return true if the *object* argument is an instance of the
*classinfo* argument, or of a (direct, indirect or *virtual*)
subclass thereof. If *object* is not an object of the given type,
the function always returns false. If *classinfo* is a tuple of
type objects (or recursively, other such tuples), return true if
*object* is an instance of any of the types. If *classinfo* is not
a type or tuple of types and such tuples, a "TypeError" exception
is raised.

issubclass(class, classinfo)

Return true if *class* is a subclass (direct, indirect or
*virtual*) of *classinfo*. A class is considered a subclass of
itself. *classinfo* may be a tuple of class objects, in which case
every entry in *classinfo* will be checked. In any other case, a
"TypeError" exception is raised.

iter(object[, sentinel])

Return an *iterator* object. The first argument is interpreted
very differently depending on the presence of the second argument.
Without a second argument, *object* must be a collection object
which supports the iteration protocol (the "__iter__()" method), or
it must support the sequence protocol (the "__getitem__()" method
with integer arguments starting at "0"). If it does not support
either of those protocols, "TypeError" is raised. If the second
argument, *sentinel*, is given, then *object* must be a callable
object. The iterator created in this case will call *object* with
no arguments for each call to its "__next__()" method; if the value
returned is equal to *sentinel*, "StopIteration" will be raised,
otherwise the value will be returned.

See also Iterator Types.

One useful application of the second form of "iter()" is to read
lines of a file until a certain line is reached. The following
example reads a file until the "readline()" method returns an empty
string:

with open('mydata.txt') as fp:
for line in iter(fp.readline, ''):
process_line(line)

len(s)

Return the length (the number of items) of an object. The argument
may be a sequence (such as a string, bytes, tuple, list, or range)
or a collection (such as a dictionary, set, or frozen set).

class list([iterable])

Rather than being a function, "list" is actually a mutable sequence
type, as documented in Lists and Sequence Types — list, tuple,
range.

locals()

Update and return a dictionary representing the current local
symbol table. Free variables are returned by "locals()" when it is
called in function blocks, but not in class blocks.

Note: The contents of this dictionary should not be modified;
changes may not affect the values of local and free variables
used by the interpreter.

map(function, iterable, ...)

Return an iterator that applies *function* to every item of
*iterable*, yielding the results. If additional *iterable*
arguments are passed, *function* must take that many arguments and
is applied to the items from all iterables in parallel. With
multiple iterables, the iterator stops when the shortest iterable
is exhausted. For cases where the function inputs are already
arranged into argument tuples, see "itertools.starmap()".

max(iterable, *[, key, default])
max(arg1, arg2, *args[, key])

Return the largest item in an iterable or the largest of two or
more arguments.

If one positional argument is provided, it should be an *iterable*.
The largest item in the iterable is returned. If two or more
positional arguments are provided, the largest of the positional
arguments is returned.

There are two optional keyword-only arguments. The *key* argument
specifies a one-argument ordering function like that used for
"list.sort()". The *default* argument specifies an object to return
if the provided iterable is empty. If the iterable is empty and
*default* is not provided, a "ValueError" is raised.

If multiple items are maximal, the function returns the first one
encountered. This is consistent with other sort-stability
preserving tools such as "sorted(iterable, key=keyfunc,
reverse=True)[0]" and "heapq.nlargest(1, iterable, key=keyfunc)".

New in version 3.4: The *default* keyword-only argument.

memoryview(obj)

Return a “memory view” object created from the given argument. See
Memory Views for more information.

min(iterable, *[, key, default])
min(arg1, arg2, *args[, key])

Return the smallest item in an iterable or the smallest of two or
more arguments.

If one positional argument is provided, it should be an *iterable*.
The smallest item in the iterable is returned. If two or more
positional arguments are provided, the smallest of the positional
arguments is returned.

If multiple items are minimal, the function returns the first one
encountered. This is consistent with other sort-stability
preserving tools such as "sorted(iterable, key=keyfunc)[0]" and
"heapq.nsmallest(1, iterable, key=keyfunc)".

New in version 3.4: The *default* keyword-only argument.

next(iterator[, default])

Retrieve the next item from the *iterator* by calling its
"__next__()" method. If *default* is given, it is returned if the
iterator is exhausted, otherwise "StopIteration" is raised.

class object

Return a new featureless object. "object" is a base for all
classes. It has the methods that are common to all instances of
Python classes. This function does not accept any arguments.

Note: "object" does *not* have a "__dict__", so you can’t assign
arbitrary attributes to an instance of the "object" class.

oct(x)

Convert an integer number to an octal string prefixed with “0o”.
The result is a valid Python expression. If *x* is not a Python
"int" object, it has to define an "__index__()" method that returns
an integer. For example:

>>> oct(8)
'0o10'
>>> oct(-56)
'-0o70'

If you want to convert an integer number to octal string either
with prefix “0o” or not, you can use either of the following ways.

>>> '%#o' % 10, '%o' % 10
('0o12', '12')
>>> format(10, '#o'), format(10, 'o')
('0o12', '12')
>>> f'{10:#o}', f'{10:o}'
('0o12', '12')

See also "format()" for more information.

open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

Open *file* and return a corresponding *file object*. If the file
cannot be opened, an "OSError" is raised.

*file* is a *path-like object* giving the pathname (absolute or
relative to the current working directory) of the file to be opened
or an integer file descriptor of the file to be wrapped. (If a
file descriptor is given, it is closed when the returned I/O object
is closed, unless *closefd* is set to "False".)

*mode* is an optional string that specifies the mode in which the
file is opened. It defaults to "'r'" which means open for reading
in text mode. Other common values are "'w'" for writing (truncating
the file if it already exists), "'x'" for exclusive creation and
"'a'" for appending (which on *some* Unix systems, means that *all*
writes append to the end of the file regardless of the current seek
position). In text mode, if *encoding* is not specified the
encoding used is platform dependent:
"locale.getpreferredencoding(False)" is called to get the current
locale encoding. (For reading and writing raw bytes use binary mode
and leave *encoding* unspecified.) The available modes are:

+-----------+-----------------------------------------------------------------+
| Character | Meaning |
+===========+=================================================================+
| "'r'" | open for reading (default) |
+-----------+-----------------------------------------------------------------+
| "'w'" | open for writing, truncating the file first |
+-----------+-----------------------------------------------------------------+
| "'x'" | open for exclusive creation, failing if the file already exists |
+-----------+-----------------------------------------------------------------+
| "'a'" | open for writing, appending to the end of the file if it exists |
+-----------+-----------------------------------------------------------------+
| "'b'" | binary mode |
+-----------+-----------------------------------------------------------------+
| "'t'" | text mode (default) |
+-----------+-----------------------------------------------------------------+
| "'+'" | open a disk file for updating (reading and writing) |
+-----------+-----------------------------------------------------------------+
| "'U'" | *universal newlines* mode (deprecated) |
+-----------+-----------------------------------------------------------------+

The default mode is "'r'" (open for reading text, synonym of
"'rt'"). For binary read-write access, the mode "'w+b'" opens and
truncates the file to 0 bytes. "'r+b'" opens the file without
truncation.

As mentioned in the Overview, Python distinguishes between binary
and text I/O. Files opened in binary mode (including "'b'" in the
*mode* argument) return contents as "bytes" objects without any
decoding. In text mode (the default, or when "'t'" is included in
the *mode* argument), the contents of the file are returned as
"str", the bytes having been first decoded using a platform-
dependent encoding or using the specified *encoding* if given.

Note: Python doesn’t depend on the underlying operating system’s
notion of text files; all the processing is done by Python
itself, and is therefore platform-independent.

*buffering* is an optional integer used to set the buffering
policy. Pass 0 to switch buffering off (only allowed in binary
mode), 1 to select line buffering (only usable in text mode), and
an integer > 1 to indicate the size in bytes of a fixed-size chunk
buffer. When no *buffering* argument is given, the default
buffering policy works as follows:

* Binary files are buffered in fixed-size chunks; the size of the
buffer is chosen using a heuristic trying to determine the
underlying device’s “block size” and falling back on
"io.DEFAULT_BUFFER_SIZE". On many systems, the buffer will
typically be 4096 or 8192 bytes long.

* “Interactive” text files (files for which "isatty()" returns
"True") use line buffering. Other text files use the policy
described above for binary files.

*encoding* is the name of the encoding used to decode or encode the
file. This should only be used in text mode. The default encoding
is platform dependent (whatever "locale.getpreferredencoding()"
returns), but any *text encoding* supported by Python can be used.
See the "codecs" module for the list of supported encodings.

*errors* is an optional string that specifies how encoding and
decoding errors are to be handled—this cannot be used in binary
mode. A variety of standard error handlers are available (listed
under Error Handlers), though any error handling name that has been
registered with "codecs.register_error()" is also valid. The
standard names include:

* "'strict'" to raise a "ValueError" exception if there is an
encoding error. The default value of "None" has the same effect.

* "'ignore'" ignores errors. Note that ignoring encoding errors
can lead to data loss.

* "'replace'" causes a replacement marker (such as "'?'") to be
inserted where there is malformed data.

* "'surrogateescape'" will represent any incorrect bytes as code
points in the Unicode Private Use Area ranging from U+DC80 to
U+DCFF. These private code points will then be turned back into
the same bytes when the "surrogateescape" error handler is used
when writing data. This is useful for processing files in an
unknown encoding.

* "'xmlcharrefreplace'" is only supported when writing to a file.
Characters not supported by the encoding are replaced with the
appropriate XML character reference "&#nnn;".

* "'backslashreplace'" replaces malformed data by Python’s
backslashed escape sequences.

* "'namereplace'" (also only supported when writing) replaces
unsupported characters with "\N{...}" escape sequences.

*newline* controls how *universal newlines* mode works (it only
applies to text mode). It can be "None", "''", "'\n'", "'\r'", and
"'\r\n'". It works as follows:

* When reading input from the stream, if *newline* is "None",
universal newlines mode is enabled. Lines in the input can end
in "'\n'", "'\r'", or "'\r\n'", and these are translated into
"'\n'" before being returned to the caller. If it is "''",
universal newlines mode is enabled, but line endings are returned
to the caller untranslated. If it has any of the other legal
values, input lines are only terminated by the given string, and
the line ending is returned to the caller untranslated.

* When writing output to the stream, if *newline* is "None", any
"'\n'" characters written are translated to the system default
line separator, "os.linesep". If *newline* is "''" or "'\n'", no
translation takes place. If *newline* is any of the other legal
values, any "'\n'" characters written are translated to the given
string.

If *closefd* is "False" and a file descriptor rather than a
filename was given, the underlying file descriptor will be kept
open when the file is closed. If a filename is given *closefd*
must be "True" (the default) otherwise an error will be raised.

A custom opener can be used by passing a callable as *opener*. The
underlying file descriptor for the file object is then obtained by
calling *opener* with (*file*, *flags*). *opener* must return an
open file descriptor (passing "os.open" as *opener* results in
functionality similar to passing "None").

The newly created file is non-inheritable.

The following example uses the dir_fd parameter of the "os.open()"
function to open a file relative to a given directory:

>>> import os
>>> dir_fd = os.open('somedir', os.O_RDONLY)
>>> def opener(path, flags):
... return os.open(path, flags, dir_fd=dir_fd)
...
>>> with open('spamspam.txt', 'w', opener=opener) as f:
... print('This will be written to somedir/spamspam.txt', file=f)
...
>>> os.close(dir_fd) # don't leak a file descriptor

The type of *file object* returned by the "open()" function depends
on the mode. When "open()" is used to open a file in a text mode
("'w'", "'r'", "'wt'", "'rt'", etc.), it returns a subclass of
"io.TextIOBase" (specifically "io.TextIOWrapper"). When used to
open a file in a binary mode with buffering, the returned class is
a subclass of "io.BufferedIOBase". The exact class varies: in read
binary mode, it returns an "io.BufferedReader"; in write binary and
append binary modes, it returns an "io.BufferedWriter", and in
read/write mode, it returns an "io.BufferedRandom". When buffering
is disabled, the raw stream, a subclass of "io.RawIOBase",
"io.FileIO", is returned.

See also the file handling modules, such as, "fileinput", "io"
(where "open()" is declared), "os", "os.path", "tempfile", and
"shutil".

Changed in version 3.3:

* The *opener* parameter was added.

* The "'x'" mode was added.

* "IOError" used to be raised, it is now an alias of
"OSError".

* "FileExistsError" is now raised if the file opened in
exclusive creation mode ("'x'") already exists.

Changed in version 3.4:

* The file is now non-inheritable.

Deprecated since version 3.4, will be removed in version 4.0: The
"'U'" mode.

Changed in version 3.5:

* If the system call is interrupted and the signal handler
does not raise an exception, the function now retries the
system call instead of raising an "InterruptedError" exception
(see **PEP 475** for the rationale).

* The "'namereplace'" error handler was added.

Changed in version 3.6:

* Support added to accept objects implementing "os.PathLike".

* On Windows, opening a console buffer may return a subclass
of "io.RawIOBase" other than "io.FileIO".

ord(c)

Given a string representing one Unicode character, return an
integer representing the Unicode code point of that character. For
example, "ord('a')" returns the integer "97" and "ord('€')" (Euro
sign) returns "8364". This is the inverse of "chr()".

pow(x, y[, z])

Return *x* to the power *y*; if *z* is present, return *x* to the
power *y*, modulo *z* (computed more efficiently than "pow(x, y) %
z"). The two-argument form "pow(x, y)" is equivalent to using the
power operator: "x**y".

The arguments must have numeric types. With mixed operand types,
the coercion rules for binary arithmetic operators apply. For
"int" operands, the result has the same type as the operands (after
coercion) unless the second argument is negative; in that case, all
arguments are converted to float and a float result is delivered.
For example, "10**2" returns "100", but "10**-2" returns "0.01".
If the second argument is negative, the third argument must be
omitted. If *z* is present, *x* and *y* must be of integer types,
and *y* must be non-negative.

print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

Print *objects* to the text stream *file*, separated by *sep* and
followed by *end*. *sep*, *end*, *file* and *flush*, if present,
must be given as keyword arguments.

All non-keyword arguments are converted to strings like "str()"
does and written to the stream, separated by *sep* and followed by
*end*. Both *sep* and *end* must be strings; they can also be
"None", which means to use the default values. If no *objects* are
given, "print()" will just write *end*.

The *file* argument must be an object with a "write(string)"
method; if it is not present or "None", "sys.stdout" will be used.
Since printed arguments are converted to text strings, "print()"
cannot be used with binary mode file objects. For these, use
"file.write(...)" instead.

Whether output is buffered is usually determined by *file*, but if
the *flush* keyword argument is true, the stream is forcibly
flushed.

Changed in version 3.3: Added the *flush* keyword argument.

class property(fget=None, fset=None, fdel=None, doc=None)

Return a property attribute.

*fget* is a function for getting an attribute value. *fset* is a
function for setting an attribute value. *fdel* is a function for
deleting an attribute value. And *doc* creates a docstring for the
attribute.

A typical use is to define a managed attribute "x":

class C:
def __init__(self):
self._x = None

def getx(self):
return self._x

def setx(self, value):
self._x = value

def delx(self):
del self._x

x = property(getx, setx, delx, "I'm the 'x' property.")

If *c* is an instance of *C*, "c.x" will invoke the getter, "c.x =
value" will invoke the setter and "del c.x" the deleter.

If given, *doc* will be the docstring of the property attribute.
Otherwise, the property will copy *fget*’s docstring (if it
exists). This makes it possible to create read-only properties
easily using "property()" as a *decorator*:

class Parrot:
def __init__(self):
self._voltage = 100000

@property
def voltage(self):
"""Get the current voltage."""
return self._voltage

The "@property" decorator turns the "voltage()" method into a
“getter” for a read-only attribute with the same name, and it sets
the docstring for *voltage* to “Get the current voltage.”

A property object has "getter", "setter", and "deleter" methods
usable as decorators that create a copy of the property with the
corresponding accessor function set to the decorated function.
This is best explained with an example:

class C:
def __init__(self):
self._x = None

@property
def x(self):
"""I'm the 'x' property."""
return self._x

@x.setter
def x(self, value):
self._x = value

@x.deleter
def x(self):
del self._x

This code is exactly equivalent to the first example. Be sure to
give the additional functions the same name as the original
property ("x" in this case.)

The returned property object also has the attributes "fget",
"fset", and "fdel" corresponding to the constructor arguments.

Changed in version 3.5: The docstrings of property objects are now
writeable.

range(stop)
range(start, stop[, step])

Rather than being a function, "range" is actually an immutable
sequence type, as documented in Ranges and Sequence Types — list,
tuple, range.

repr(object)

Return a string containing a printable representation of an object.
For many types, this function makes an attempt to return a string
that would yield an object with the same value when passed to
"eval()", otherwise the representation is a string enclosed in
angle brackets that contains the name of the type of the object
together with additional information often including the name and
address of the object. A class can control what this function
returns for its instances by defining a "__repr__()" method.

reversed(seq)

Return a reverse *iterator*. *seq* must be an object which has a
"__reversed__()" method or supports the sequence protocol (the
"__len__()" method and the "__getitem__()" method with integer
arguments starting at "0").

round(number[, ndigits])

Return *number* rounded to *ndigits* precision after the decimal
point. If *ndigits* is omitted or is "None", it returns the
nearest integer to its input.

For the built-in types supporting "round()", values are rounded to
the closest multiple of 10 to the power minus *ndigits*; if two
multiples are equally close, rounding is done toward the even
choice (so, for example, both "round(0.5)" and "round(-0.5)" are
"0", and "round(1.5)" is "2"). Any integer value is valid for
*ndigits* (positive, zero, or negative). The return value is an
integer if called with one argument, otherwise of the same type as
*number*.

For a general Python object "number", "round(number, ndigits)"
delegates to "number.__round__(ndigits)".

Note: The behavior of "round()" for floats can be surprising: for
example, "round(2.675, 2)" gives "2.67" instead of the expected
"2.68". This is not a bug: it’s a result of the fact that most
decimal fractions can’t be represented exactly as a float. See
Floating Point Arithmetic: Issues and Limitations for more
information.

class set([iterable])

Return a new "set" object, optionally with elements taken from
*iterable*. "set" is a built-in class. See "set" and Set Types —
set, frozenset for documentation about this class.

For other containers see the built-in "frozenset", "list", "tuple",
and "dict" classes, as well as the "collections" module.

setattr(object, name, value)

This is the counterpart of "getattr()". The arguments are an
object, a string and an arbitrary value. The string may name an
existing attribute or a new attribute. The function assigns the
value to the attribute, provided the object allows it. For
example, "setattr(x, 'foobar', 123)" is equivalent to "x.foobar =
123".

class slice(stop)
class slice(start, stop[, step])

Return a *slice* object representing the set of indices specified
by "range(start, stop, step)". The *start* and *step* arguments
default to "None". Slice objects have read-only data attributes
"start", "stop" and "step" which merely return the argument values
(or their default). They have no other explicit functionality;
however they are used by Numerical Python and other third party
extensions. Slice objects are also generated when extended indexing
syntax is used. For example: "a[start:stop:step]" or
"a[start:stop, i]". See "itertools.islice()" for an alternate
version that returns an iterator.

sorted(iterable, *, key=None, reverse=False)

Return a new sorted list from the items in *iterable*.

Has two optional arguments which must be specified as keyword
arguments.

*key* specifies a function of one argument that is used to extract
a comparison key from each list element: "key=str.lower". The
default value is "None" (compare the elements directly).

*reverse* is a boolean value. If set to "True", then the list
elements are sorted as if each comparison were reversed.

Use "functools.cmp_to_key()" to convert an old-style *cmp* function
to a *key* function.

The built-in "sorted()" function is guaranteed to be stable. A sort
is stable if it guarantees not to change the relative order of
elements that compare equal — this is helpful for sorting in
multiple passes (for example, sort by department, then by salary
grade).

For sorting examples and a brief sorting tutorial, see Sorting HOW
TO.

@staticmethod

Transform a method into a static method.

A static method does not receive an implicit first argument. To
declare a static method, use this idiom:

class C:
@staticmethod
def f(arg1, arg2, ...): ...

The "@staticmethod" form is a function *decorator* – see the
description of function definitions in Function definitions for
details.

It can be called either on the class (such as "C.f()") or on an
instance (such as "C().f()"). The instance is ignored except for
its class.

Static methods in Python are similar to those found in Java or C++.
Also see "classmethod()" for a variant that is useful for creating
alternate class constructors.

Like all decorators, it is also possible to call "staticmethod" as
a regular function and do something with its result. This is
needed in some cases where you need a reference to a function from
a class body and you want to avoid the automatic transformation to
instance method. For these cases, use this idiom:

class C:
builtin_open = staticmethod(open)

For more information on static methods, consult the documentation
on the standard type hierarchy in The standard type hierarchy.

class str(object='')
class str(object=b'', encoding='utf-8', errors='strict')

Return a "str" version of *object*. See "str()" for details.

"str" is the built-in string *class*. For general information
about strings, see Text Sequence Type — str.

sum(iterable[, start])

Sums *start* and the items of an *iterable* from left to right and
returns the total. *start* defaults to "0". The *iterable*’s items
are normally numbers, and the start value is not allowed to be a
string.

For some use cases, there are good alternatives to "sum()". The
preferred, fast way to concatenate a sequence of strings is by
calling "''.join(sequence)". To add floating point values with
extended precision, see "math.fsum()". To concatenate a series of
iterables, consider using "itertools.chain()".

super([type[, object-or-type]])

Return a proxy object that delegates method calls to a parent or
sibling class of *type*. This is useful for accessing inherited
methods that have been overridden in a class. The search order is
same as that used by "getattr()" except that the *type* itself is
skipped.

The "__mro__" attribute of the *type* lists the method resolution
search order used by both "getattr()" and "super()". The attribute
is dynamic and can change whenever the inheritance hierarchy is
updated.

If the second argument is omitted, the super object returned is
unbound. If the second argument is an object, "isinstance(obj,
type)" must be true. If the second argument is a type,
"issubclass(type2, type)" must be true (this is useful for
classmethods).

There are two typical use cases for *super*. In a class hierarchy
with single inheritance, *super* can be used to refer to parent
classes without naming them explicitly, thus making the code more
maintainable. This use closely parallels the use of *super* in
other programming languages.

The second use case is to support cooperative multiple inheritance
in a dynamic execution environment. This use case is unique to
Python and is not found in statically compiled languages or
languages that only support single inheritance. This makes it
possible to implement “diamond diagrams” where multiple base
classes implement the same method. Good design dictates that this
method have the same calling signature in every case (because the
order of calls is determined at runtime, because that order adapts
to changes in the class hierarchy, and because that order can
include sibling classes that are unknown prior to runtime).

For both use cases, a typical superclass call looks like this:

class C(B):
def method(self, arg):
super().method(arg) # This does the same thing as:
# super(C, self).method(arg)

Note that "super()" is implemented as part of the binding process
for explicit dotted attribute lookups such as
"super().__getitem__(name)". It does so by implementing its own
"__getattribute__()" method for searching classes in a predictable
order that supports cooperative multiple inheritance. Accordingly,
"super()" is undefined for implicit lookups using statements or
operators such as "super()[name]".

Also note that, aside from the zero argument form, "super()" is not
limited to use inside methods. The two argument form specifies the
arguments exactly and makes the appropriate references. The zero
argument form only works inside a class definition, as the compiler
fills in the necessary details to correctly retrieve the class
being defined, as well as accessing the current instance for
ordinary methods.

For practical suggestions on how to design cooperative classes
using "super()", see guide to using super().

tuple([iterable])

Rather than being a function, "tuple" is actually an immutable
sequence type, as documented in Tuples and Sequence Types — list,
tuple, range.

class type(object)
class type(name, bases, dict)

With one argument, return the type of an *object*. The return
value is a type object and generally the same object as returned by
"object.__class__".

The "isinstance()" built-in function is recommended for testing the
type of an object, because it takes subclasses into account.

With three arguments, return a new type object. This is
essentially a dynamic form of the "class" statement. The *name*
string is the class name and becomes the "__name__" attribute; the
*bases* tuple itemizes the base classes and becomes the "__bases__"
attribute; and the *dict* dictionary is the namespace containing
definitions for class body and is copied to a standard dictionary
to become the "__dict__" attribute. For example, the following two
statements create identical "type" objects:

>>> class X:
... a = 1
...
>>> X = type('X', (object,), dict(a=1))