The PyArg_ParseTuple() function is declared as follows:
int PyArg_ParseTuple(PyObject *arg, char *format, ...);
The arg argument must be a tuple object containing an argument list passed from Python to a C function. The format argument must be a format string, whose syntax is explained below. The remaining arguments must be addresses of variables whose type is determined by the format string. For the conversion to succeed, the arg object must match the format and the format must be exhausted.
Note that while PyArg_ParseTuple() checks that the Python arguments have the required types, it cannot check the validity of the addresses of C variables passed to the call: if you make mistakes there, your code will probably crash or at least overwrite random bits in memory. So be careful!
A format string consists of zero or more ``format units''. A format unit describes one Python object; it is usually a single character or a parenthesized sequence of format units. With a fe
w exceptions, a format unit that is not a parenthesized sequence normally corresponds to a single address argument to PyArg_ParseTuple(). In the following description, the quoted form is the format unit; the entry in (round) parentheses is the Python object type that matches the format unit; and the entry in [square] brackets is the type of the C variable(s) whose address should be passed. (Use the "&"operator to pass a variable's address.)
Note that any Python object references which are provided to the caller are borrowed references; do not decrement their reference count!
"s" (string or Unicode object) [char *]
Convert a Python string or Unicode object to a C pointer to a character string. You must not provide storage for the string itself; a pointer to an existing string is stored into the character pointer variable whose address you pass. The C string is null-terminated. The Python string must not contain embedded null bytes; if it does, a TypeError exception is raised. Unicode objects are converted to C strings using the default encoding. If this conversion fails, an UnicodeError is raised.
"s#" (string, Unicode or any read buffer compatible object) [char *, int]
This variant on "s" stores into two C variables, the first one a pointer to a character string, the second one its length. In this case the Python string may contain embedded null bytes. Unicode objects pass back a pointer to the default encoded string version of the object if such a conversion is possible. All other read buffer compatible objects pass back a reference to the raw internal data representation.
"z" (string or None) [char *]
Like "s", but the Python object may also be None, in which case the C pointer is set to NULL.
"z#" (string or None or any read buffer compatible object) [char *, int]
This is to "s#" as "z" is to "s".
"u" (Unicode object) [Py_UNICODE *]python round函数怎么使用
Convert a Python Unicode object to a C pointer to a null-terminated buffer of 16-bit Unicode (UTF-16) data. As with "s", there is no need to provide storage for the Unicode data buffer; a pointer to the existing Unicode data is stored into the Py_UNICODE pointer variable whose address you pass.
"u#" (Unicode object) [Py_UNICODE *, int]
This variant on "u" stores into two C variables, the first one a pointer to a Unicode data buffer, the second one its length.
"es" (string, Unicode object or character buffer compatible object) [const char *encoding, char **buffer]
This variant on "s" is used for encoding Unicode and objects convertible to Unicode into a character buffer. It only works for encoded data without embedded NULL bytes.
The variant reads one C variable and stores into two C variables, the first one a pointer to an encoding name string (encoding), the second a pointer to a pointer to a character buffer
(**buffer, the buffer used for storing the encoded data) and the third one a pointer to an integer (*buffer_length, the buffer length).
The encoding name must map to a registered codec. If set to NULL, the default encoding is used.
PyArg_ParseTuple() will allocate a buffer of the needed size using PyMem_NEW(), copy the encoded data into this buffer and adjust *buffer to reference the newly allocated storage. The caller is responsible for calling PyMem_Free() to free the allocated buffer after usage.
"es#" (string, Unicode object or character buffer compatible object) [const char *encoding, char **buffer, int *buffer_length]
This variant on "s#" is used for encoding Unicode and objects convertible to Unicode into a character buffer. It reads one C variable and stores into two C variables, the first one a pointer to an encoding name string (encoding), the second a pointer to a pointer to a chara
cter buffer (**buffer, the buffer used for storing the encoded data) and the third one a pointer to an integer (*buffer_length, the buffer length).
The encoding name must map to a registered codec. If set to NULL, the default encoding is used.
There are two modes of operation:
If *buffer points a NULL pointer, PyArg_ParseTuple() will allocate a buffer of the needed size using PyMem_NEW(), copy the encoded data into this buffer and adjust *buffer to reference the newly allocated storage. The caller is responsible for calling PyMem_Free() to free the allocated buffer after usage.

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