Python 3.6.5 Documentation >  Bytes Objects

Bytes Objects
*************

These functions raise "TypeError" when expecting a bytes parameter and
are called with a non-bytes parameter.

PyBytesObject

This subtype of "PyObject" represents a Python bytes object.

PyTypeObject PyBytes_Type

This instance of "PyTypeObject" represents the Python bytes type;
it is the same object as "bytes" in the Python layer.

int PyBytes_Check(PyObject *o)

Return true if the object *o* is a bytes object or an instance of a
subtype of the bytes type.

int PyBytes_CheckExact(PyObject *o)

Return true if the object *o* is a bytes object, but not an
instance of a subtype of the bytes type.

PyObject* PyBytes_FromString(const char *v)

Return a new bytes object with a copy of the string *v* as value on
success, and *NULL* on failure. The parameter *v* must not be
*NULL*; it will not be checked.

PyObject* PyBytes_FromStringAndSize(const char *v, Py_ssize_t len)

Return a new bytes object with a copy of the string *v* as value
and length *len* on success, and *NULL* on failure. If *v* is
*NULL*, the contents of the bytes object are uninitialized.

PyObject* PyBytes_FromFormat(const char *format, ...)

Take a C "printf()"-style *format* string and a variable number of
arguments, calculate the size of the resulting Python bytes object
and return a bytes object with the values formatted into it. The
variable arguments must be C types and must correspond exactly to
the format characters in the *format* string. The following format
characters are allowed:

+---------------------+-----------------+----------------------------------+
| Format Characters | Type | Comment |
+=====================+=================+==================================+
| "%%" | *n/a* | The literal % character. |
+---------------------+-----------------+----------------------------------+
| "%c" | int | A single byte, represented as a |
| | | C int. |
+---------------------+-----------------+----------------------------------+
| "%d" | int | Exactly equivalent to |
| | | "printf("%d")". |
+---------------------+-----------------+----------------------------------+
| "%u" | unsigned int | Exactly equivalent to |
| | | "printf("%u")". |
+---------------------+-----------------+----------------------------------+
| "%ld" | long | Exactly equivalent to |
| | | "printf("%ld")". |
+---------------------+-----------------+----------------------------------+
| "%lu" | unsigned long | Exactly equivalent to |
| | | "printf("%lu")". |
+---------------------+-----------------+----------------------------------+
| "%zd" | Py_ssize_t | Exactly equivalent to |
| | | "printf("%zd")". |
+---------------------+-----------------+----------------------------------+
| "%zu" | size_t | Exactly equivalent to |
| | | "printf("%zu")". |
+---------------------+-----------------+----------------------------------+
| "%i" | int | Exactly equivalent to |
| | | "printf("%i")". |
+---------------------+-----------------+----------------------------------+
| "%x" | int | Exactly equivalent to |
| | | "printf("%x")". |
+---------------------+-----------------+----------------------------------+
| "%s" | char* | A null-terminated C character |
| | | array. |
+---------------------+-----------------+----------------------------------+
| "%p" | void* | The hex representation of a C |
| | | pointer. Mostly equivalent to |
| | | "printf("%p")" except that it is |
| | | guaranteed to start with the |
| | | literal "0x" regardless of what |
| | | the platform’s "printf" yields. |
+---------------------+-----------------+----------------------------------+

An unrecognized format character causes all the rest of the format
string to be copied as-is to the result object, and any extra
arguments discarded.

PyObject* PyBytes_FromFormatV(const char *format, va_list vargs)

Identical to "PyBytes_FromFormat()" except that it takes exactly
two arguments.

PyObject* PyBytes_FromObject(PyObject *o)

Return the bytes representation of object *o* that implements the
buffer protocol.

Py_ssize_t PyBytes_Size(PyObject *o)

Return the length of the bytes in bytes object *o*.

Py_ssize_t PyBytes_GET_SIZE(PyObject *o)

Macro form of "PyBytes_Size()" but without error checking.

char* PyBytes_AsString(PyObject *o)

Return a pointer to the contents of *o*. The pointer refers to the
internal buffer of *o*, which consists of "len(o) + 1" bytes. The
last byte in the buffer is always null, regardless of whether there
are any other null bytes. The data must not be modified in any
way, unless the object was just created using
"PyBytes_FromStringAndSize(NULL, size)". It must not be
deallocated. If *o* is not a bytes object at all,
"PyBytes_AsString()" returns *NULL* and raises "TypeError".

char* PyBytes_AS_STRING(PyObject *string)

Macro form of "PyBytes_AsString()" but without error checking.

int PyBytes_AsStringAndSize(PyObject *obj, char **buffer, Py_ssize_t *length)

Return the null-terminated contents of the object *obj* through the
output variables *buffer* and *length*.

If *length* is *NULL*, the bytes object may not contain embedded
null bytes; if it does, the function returns "-1" and a
"ValueError" is raised.

The buffer refers to an internal buffer of *obj*, which includes an
additional null byte at the end (not counted in *length*). The
data must not be modified in any way, unless the object was just
created using "PyBytes_FromStringAndSize(NULL, size)". It must not
be deallocated. If *obj* is not a bytes object at all,
"PyBytes_AsStringAndSize()" returns "-1" and raises "TypeError".

Changed in version 3.5: Previously, "TypeError" was raised when
embedded null bytes were encountered in the bytes object.

void PyBytes_Concat(PyObject **bytes, PyObject *newpart)

Create a new bytes object in **bytes* containing the contents of
*newpart* appended to *bytes*; the caller will own the new
reference. The reference to the old value of *bytes* will be
stolen. If the new object cannot be created, the old reference to
*bytes* will still be discarded and the value of **bytes* will be
set to *NULL*; the appropriate exception will be set.

void PyBytes_ConcatAndDel(PyObject **bytes, PyObject *newpart)

Create a new bytes object in **bytes* containing the contents of
*newpart* appended to *bytes*. This version decrements the
reference count of *newpart*.

int _PyBytes_Resize(PyObject **bytes, Py_ssize_t newsize)

A way to resize a bytes object even though it is “immutable”. Only
use this to build up a brand new bytes object; don’t use this if
the bytes may already be known in other parts of the code. It is
an error to call this function if the refcount on the input bytes
object is not one. Pass the address of an existing bytes object as
an lvalue (it may be written into), and the new size desired. On
success, **bytes* holds the resized bytes object and "0" is
returned; the address in **bytes* may differ from its input value.
If the reallocation fails, the original bytes object at **bytes* is
deallocated, **bytes* is set to *NULL*, "MemoryError" is set, and
"-1" is returned.