mirror of
https://github.com/python/cpython.git
synced 2024-11-28 16:45:42 +01:00
132 lines
5.4 KiB
ReStructuredText
132 lines
5.4 KiB
ReStructuredText
.. highlightlang:: c
|
|
|
|
.. _string-conversion:
|
|
|
|
String conversion and formatting
|
|
================================
|
|
|
|
Functions for number conversion and formatted string output.
|
|
|
|
|
|
.. c:function:: int PyOS_snprintf(char *str, size_t size, const char *format, ...)
|
|
|
|
Output not more than *size* bytes to *str* according to the format string
|
|
*format* and the extra arguments. See the Unix man page :manpage:`snprintf(2)`.
|
|
|
|
|
|
.. c:function:: int PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va)
|
|
|
|
Output not more than *size* bytes to *str* according to the format string
|
|
*format* and the variable argument list *va*. Unix man page
|
|
:manpage:`vsnprintf(2)`.
|
|
|
|
:c:func:`PyOS_snprintf` and :c:func:`PyOS_vsnprintf` wrap the Standard C library
|
|
functions :c:func:`snprintf` and :c:func:`vsnprintf`. Their purpose is to
|
|
guarantee consistent behavior in corner cases, which the Standard C functions do
|
|
not.
|
|
|
|
The wrappers ensure that *str*[*size*-1] is always ``'\0'`` upon return. They
|
|
never write more than *size* bytes (including the trailing ``'\0'``) into str.
|
|
Both functions require that ``str != NULL``, ``size > 0`` and ``format !=
|
|
NULL``.
|
|
|
|
If the platform doesn't have :c:func:`vsnprintf` and the buffer size needed to
|
|
avoid truncation exceeds *size* by more than 512 bytes, Python aborts with a
|
|
*Py_FatalError*.
|
|
|
|
The return value (*rv*) for these functions should be interpreted as follows:
|
|
|
|
* When ``0 <= rv < size``, the output conversion was successful and *rv*
|
|
characters were written to *str* (excluding the trailing ``'\0'`` byte at
|
|
*str*[*rv*]).
|
|
|
|
* When ``rv >= size``, the output conversion was truncated and a buffer with
|
|
``rv + 1`` bytes would have been needed to succeed. *str*[*size*-1] is ``'\0'``
|
|
in this case.
|
|
|
|
* When ``rv < 0``, "something bad happened." *str*[*size*-1] is ``'\0'`` in
|
|
this case too, but the rest of *str* is undefined. The exact cause of the error
|
|
depends on the underlying platform.
|
|
|
|
The following functions provide locale-independent string to number conversions.
|
|
|
|
|
|
.. c:function:: double PyOS_string_to_double(const char *s, char **endptr, PyObject *overflow_exception)
|
|
|
|
Convert a string ``s`` to a :c:type:`double`, raising a Python
|
|
exception on failure. The set of accepted strings corresponds to
|
|
the set of strings accepted by Python's :func:`float` constructor,
|
|
except that ``s`` must not have leading or trailing whitespace.
|
|
The conversion is independent of the current locale.
|
|
|
|
If ``endptr`` is ``NULL``, convert the whole string. Raise
|
|
ValueError and return ``-1.0`` if the string is not a valid
|
|
representation of a floating-point number.
|
|
|
|
If endptr is not ``NULL``, convert as much of the string as
|
|
possible and set ``*endptr`` to point to the first unconverted
|
|
character. If no initial segment of the string is the valid
|
|
representation of a floating-point number, set ``*endptr`` to point
|
|
to the beginning of the string, raise ValueError, and return
|
|
``-1.0``.
|
|
|
|
If ``s`` represents a value that is too large to store in a float
|
|
(for example, ``"1e500"`` is such a string on many platforms) then
|
|
if ``overflow_exception`` is ``NULL`` return ``Py_HUGE_VAL`` (with
|
|
an appropriate sign) and don't set any exception. Otherwise,
|
|
``overflow_exception`` must point to a Python exception object;
|
|
raise that exception and return ``-1.0``. In both cases, set
|
|
``*endptr`` to point to the first character after the converted value.
|
|
|
|
If any other error occurs during the conversion (for example an
|
|
out-of-memory error), set the appropriate Python exception and
|
|
return ``-1.0``.
|
|
|
|
.. versionadded:: 3.1
|
|
|
|
|
|
.. c:function:: char* PyOS_double_to_string(double val, char format_code, int precision, int flags, int *ptype)
|
|
|
|
Convert a :c:type:`double` *val* to a string using supplied
|
|
*format_code*, *precision*, and *flags*.
|
|
|
|
*format_code* must be one of ``'e'``, ``'E'``, ``'f'``, ``'F'``,
|
|
``'g'``, ``'G'`` or ``'r'``. For ``'r'``, the supplied *precision*
|
|
must be 0 and is ignored. The ``'r'`` format code specifies the
|
|
standard :func:`repr` format.
|
|
|
|
*flags* can be zero or more of the values *Py_DTSF_SIGN*,
|
|
*Py_DTSF_ADD_DOT_0*, or *Py_DTSF_ALT*, or-ed together:
|
|
|
|
* *Py_DTSF_SIGN* means to always precede the returned string with a sign
|
|
character, even if *val* is non-negative.
|
|
|
|
* *Py_DTSF_ADD_DOT_0* means to ensure that the returned string will not look
|
|
like an integer.
|
|
|
|
* *Py_DTSF_ALT* means to apply "alternate" formatting rules. See the
|
|
documentation for the :c:func:`PyOS_snprintf` ``'#'`` specifier for
|
|
details.
|
|
|
|
If *ptype* is non-NULL, then the value it points to will be set to one of
|
|
*Py_DTST_FINITE*, *Py_DTST_INFINITE*, or *Py_DTST_NAN*, signifying that
|
|
*val* is a finite number, an infinite number, or not a number, respectively.
|
|
|
|
The return value is a pointer to *buffer* with the converted string or
|
|
*NULL* if the conversion failed. The caller is responsible for freeing the
|
|
returned string by calling :c:func:`PyMem_Free`.
|
|
|
|
.. versionadded:: 3.1
|
|
|
|
|
|
.. c:function:: char* PyOS_stricmp(char *s1, char *s2)
|
|
|
|
Case insensitive comparison of strings. The function works almost
|
|
identically to :c:func:`strcmp` except that it ignores the case.
|
|
|
|
|
|
.. c:function:: char* PyOS_strnicmp(char *s1, char *s2, Py_ssize_t size)
|
|
|
|
Case insensitive comparison of strings. The function works almost
|
|
identically to :c:func:`strncmp` except that it ignores the case.
|