Bytes Objects — Python documentation

Bytes Objects

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

type 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	Equivalent to printf("%d"). 1
%u	unsigned int	Equivalent to printf("%u"). 1
%ld	long	Equivalent to printf("%ld"). 1
%lu	unsigned long	Equivalent to printf("%lu"). 1
%zd	Py_ssize_t	Equivalent to printf("%zd"). 1
%zu	size_t	Equivalent to printf("%zu"). 1
%i	int	Equivalent to printf("%i"). 1
%x	int	Equivalent to printf("%x"). 1
%s	const char*	A null-terminated C character array.
%p	const 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.

1(1,2,3,4,5,6,7,8)

For integer specifiers (d, u, ld, lu, zd, zu, i, x): the 0-conversion flag has effect even when a precision is given.

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.