Bytes Objects¶

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

type PyBytesObject¶

This subtype of PyObject represents a Python bytes object.

PyTypeObject PyBytes_Type¶

Part of the Stable ABI.

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. This function always succeeds.

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. This function always succeeds.

PyObject *PyBytes_FromString(const char *v)¶

Return value: New reference. Part of the Stable ABI. Thread safety: Atomic.

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 value: New reference. Part of the Stable ABI. Thread safety: Atomic.

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.

Soft deprecated since version 3.15: Use the PyBytesWriter API instead of PyBytes_FromStringAndSize(NULL, len).

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

Return value: New reference. Part of the Stable ABI. Thread safety: Atomic.

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.

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

Return value: New reference. Part of the Stable ABI. Thread safety: Atomic.

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

PyObject *PyBytes_FromObject(PyObject *o)¶

Return value: New reference. Part of the Stable ABI. Thread safety: Safe for concurrent use on the same object.

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

Note

If the object implements the buffer protocol, then the buffer must not be mutated while the bytes object is being created.

Py_ssize_t PyBytes_Size(PyObject *o)¶

Part of the Stable ABI. Thread safety: Atomic.

Return the length of the bytes in bytes object o.

Py_ssize_t PyBytes_GET_SIZE(PyObject *o)¶

Thread safety: Atomic.

Similar to PyBytes_Size(), but without error checking.

char *PyBytes_AsString(PyObject *o)¶

Part of the Stable ABI. Thread safety: Safe to call from multiple threads with external synchronization only.

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)¶

Thread safety: Safe to call from multiple threads with external synchronization only.

Similar to PyBytes_AsString(), but without error checking.

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

Part of the Stable ABI. Thread safety: Safe to call from multiple threads with external synchronization only.

Return the null-terminated contents of the object obj through the output variables buffer and length. Returns 0 on success.

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)¶

Part of the Stable ABI. Thread safety: Safe for concurrent use on the same object.

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 “stolen”, the value of *bytes will be set to NULL, and the appropriate exception will be set.

Note

If newpart implements the buffer protocol, then the buffer must not be mutated while the new bytes object is being created.

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

Part of the Stable ABI. Thread safety: Safe for concurrent use on the same object.

Create a new bytes object in *bytes containing the contents of newpart appended to bytes. This version releases the strong reference to newpart (i.e. decrements its reference count).

Note

If newpart implements the buffer protocol, then the buffer must not be mutated while the new bytes object is being created.

PyObject *PyBytes_Join(PyObject *sep, PyObject *iterable)¶

Thread safety: Safe for concurrent use on the same object.

Similar to sep.join(iterable) in Python.

sep must be Python bytes object. (Note that PyUnicode_Join() accepts NULL separator and treats it as a space, whereas PyBytes_Join() doesn’t accept NULL separator.)

iterable must be an iterable object yielding objects that implement the buffer protocol.

On success, return a new bytes object. On error, set an exception and return NULL.

Added in version 3.14.

Note

If iterable objects implement the buffer protocol, then the buffers must not be mutated while the new bytes object is being created.

int _PyBytes_Resize(PyObject **bytes, Py_ssize_t newsize)¶

Thread safety: Safe to call without external synchronization on distinct objects.

Resize a bytes object. newsize will be the new length of the bytes object. You can think of it as creating a new bytes object and destroying the old one, only more efficiently.

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.

While bytes objects are usually immutable in Python, this special C API allows mutating a bytes object in-place. The returned bytes object can still be mutated using PyBytes_AsString(); except if newsize is zero in which case it returns the immutable empty bytes string.

Soft deprecated since version 3.15: Use the PyBytesWriter API instead.

PyObject *PyBytes_Repr(PyObject *bytes, int smartquotes)¶

Part of the Stable ABI. Thread safety: Atomic.

Get the string representation of bytes. This function is currently used to implement bytes.__repr__() in Python.

This function does not do type checking; it is undefined behavior to pass bytes as a non-bytes object or NULL.

If smartquotes is true, the representation will use a double-quoted string instead of single-quoted string when single-quotes are present in bytes. For example, the byte string 'Python' would be represented as b"'Python'" when smartquotes is true, or b'\'Python\'' when it is false.

On success, this function returns a strong reference to a str object containing the representation. On failure, this returns NULL with an exception set.

PyObject *PyBytes_DecodeEscape(const char *s, Py_ssize_t len, const char *errors, Py_ssize_t unicode, const char *recode_encoding)¶

Part of the Stable ABI. Thread safety: Atomic.

Unescape a backslash-escaped string s. s must not be NULL. len must be the size of s.

errors must be one of "strict", "replace", or "ignore". If errors is NULL, then "strict" is used by default.

On success, this function returns a strong reference to a Python bytes object containing the unescaped string. On failure, this function returns NULL with an exception set.

Changed in version 3.9: unicode and recode_encoding are now unused.

PyBytesWriter¶

The PyBytesWriter API can be used to create a Python bytes object.

type PyBytesWriter¶

A bytes writer object.

The API is not thread safe. To share a writer with multiple threads, a critical section or a lock is needed.

The instance must be destroyed by PyBytesWriter_Finish() on success, or PyBytesWriter_Discard() on error.

PyObject* create_abc(void)
{
    PyBytesWriter *writer = PyBytesWriter_Create(3);
    if (writer == NULL) {
        return NULL;
    }

    char *str = PyBytesWriter_GetData(writer);
    memcpy(str, "abc", 3);
    return PyBytesWriter_Finish(writer);
}

PyObject* create_abc_ptr(void)
{
    PyBytesWriter *writer = PyBytesWriter_Create(3);
    if (writer == NULL) {
        return NULL;
    }

    char *str = PyBytesWriter_GetData(writer);
    memcpy(str, "abc", 3);
    str += 3;
    return PyBytesWriter_FinishWithPointer(writer, str);
}

int copy_bytes(char *dest, const char *src, Py_ssize_t num_bytes)
{
    ...
}

PyObject* create_string(const char *start, Py_ssize_t num_bytes)
{
    PyObject *result = PyBytes_FromStringAndSize(NULL, num_bytes);
    if (result == NULL) {
        return NULL;
    }
    if (copy_bytes(PyBytes_AS_STRING(result), start, num_bytes) < 0) {
        Py_CLEAR(result);
    }
    return result;
}

PyObject* create_string(const char *start, Py_ssize_t num_bytes)
{
    PyBytesWriter *writer = PyBytesWriter_Create(num_bytes);
    if (writer == NULL) {
        return NULL;
    }
    if (copy_bytes(PyBytesWriter_GetData(writer), start, num_bytes) < 0) {
        PyBytesWriter_Discard(writer);
        return NULL;
    }
    return PyBytesWriter_Finish(writer);
}

PyObject* create_string(Py_ssize_t size)
{
    PyObject *bytes = PyBytes_FromStringAndSize(NULL, size);
    if (bytes == NULL) {
        return NULL;
    }
    char *str = PyBytes_AS_STRING(bytes);

    // ... write data into str ...

    if (_PyBytes_Resize(&bytes, (str - PyBytes_AS_STRING(bytes)))) {
        return NULL;
    }
    return bytes;
}

PyObject* create_string(Py_ssize_t size)
{
    PyBytesWriter *writer = PyBytesWriter_Create(size);
    if (writer == NULL) {
        return NULL;
    }
    char *str = PyBytesWriter_GetData(writer);

    // ... write data into str ...

    return PyBytesWriter_FinishWithPointer(writer, str);
}