1.. highlight:: c 2 3.. _string-conversion: 4 5String conversion and formatting 6================================ 7 8Functions for number conversion and formatted string output. 9 10 11.. c:function:: int PyOS_snprintf(char *str, size_t size, const char *format, ...) 12 13 Output not more than *size* bytes to *str* according to the format string 14 *format* and the extra arguments. See the Unix man page :manpage:`snprintf(3)`. 15 16 17.. c:function:: int PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va) 18 19 Output not more than *size* bytes to *str* according to the format string 20 *format* and the variable argument list *va*. Unix man page 21 :manpage:`vsnprintf(3)`. 22 23:c:func:`PyOS_snprintf` and :c:func:`PyOS_vsnprintf` wrap the Standard C library 24functions :c:func:`snprintf` and :c:func:`vsnprintf`. Their purpose is to 25guarantee consistent behavior in corner cases, which the Standard C functions do 26not. 27 28The wrappers ensure that ``str[size-1]`` is always ``'\0'`` upon return. They 29never write more than *size* bytes (including the trailing ``'\0'``) into str. 30Both functions require that ``str != NULL``, ``size > 0``, ``format != NULL`` 31and ``size < INT_MAX``. 32 33The return value (*rv*) for these functions should be interpreted as follows: 34 35* When ``0 <= rv < size``, the output conversion was successful and *rv* 36 characters were written to *str* (excluding the trailing ``'\0'`` byte at 37 ``str[rv]``). 38 39* When ``rv >= size``, the output conversion was truncated and a buffer with 40 ``rv + 1`` bytes would have been needed to succeed. ``str[size-1]`` is ``'\0'`` 41 in this case. 42 43* When ``rv < 0``, "something bad happened." ``str[size-1]`` is ``'\0'`` in 44 this case too, but the rest of *str* is undefined. The exact cause of the error 45 depends on the underlying platform. 46 47 48The following functions provide locale-independent string to number conversions. 49 50.. c:function:: double PyOS_string_to_double(const char *s, char **endptr, PyObject *overflow_exception) 51 52 Convert a string ``s`` to a :c:type:`double`, raising a Python 53 exception on failure. The set of accepted strings corresponds to 54 the set of strings accepted by Python's :func:`float` constructor, 55 except that ``s`` must not have leading or trailing whitespace. 56 The conversion is independent of the current locale. 57 58 If ``endptr`` is ``NULL``, convert the whole string. Raise 59 :exc:`ValueError` and return ``-1.0`` if the string is not a valid 60 representation of a floating-point number. 61 62 If endptr is not ``NULL``, convert as much of the string as 63 possible and set ``*endptr`` to point to the first unconverted 64 character. If no initial segment of the string is the valid 65 representation of a floating-point number, set ``*endptr`` to point 66 to the beginning of the string, raise ValueError, and return 67 ``-1.0``. 68 69 If ``s`` represents a value that is too large to store in a float 70 (for example, ``"1e500"`` is such a string on many platforms) then 71 if ``overflow_exception`` is ``NULL`` return ``Py_HUGE_VAL`` (with 72 an appropriate sign) and don't set any exception. Otherwise, 73 ``overflow_exception`` must point to a Python exception object; 74 raise that exception and return ``-1.0``. In both cases, set 75 ``*endptr`` to point to the first character after the converted value. 76 77 If any other error occurs during the conversion (for example an 78 out-of-memory error), set the appropriate Python exception and 79 return ``-1.0``. 80 81 .. versionadded:: 3.1 82 83 84.. c:function:: char* PyOS_double_to_string(double val, char format_code, int precision, int flags, int *ptype) 85 86 Convert a :c:type:`double` *val* to a string using supplied 87 *format_code*, *precision*, and *flags*. 88 89 *format_code* must be one of ``'e'``, ``'E'``, ``'f'``, ``'F'``, 90 ``'g'``, ``'G'`` or ``'r'``. For ``'r'``, the supplied *precision* 91 must be 0 and is ignored. The ``'r'`` format code specifies the 92 standard :func:`repr` format. 93 94 *flags* can be zero or more of the values ``Py_DTSF_SIGN``, 95 ``Py_DTSF_ADD_DOT_0``, or ``Py_DTSF_ALT``, or-ed together: 96 97 * ``Py_DTSF_SIGN`` means to always precede the returned string with a sign 98 character, even if *val* is non-negative. 99 100 * ``Py_DTSF_ADD_DOT_0`` means to ensure that the returned string will not look 101 like an integer. 102 103 * ``Py_DTSF_ALT`` means to apply "alternate" formatting rules. See the 104 documentation for the :c:func:`PyOS_snprintf` ``'#'`` specifier for 105 details. 106 107 If *ptype* is non-``NULL``, then the value it points to will be set to one of 108 ``Py_DTST_FINITE``, ``Py_DTST_INFINITE``, or ``Py_DTST_NAN``, signifying that 109 *val* is a finite number, an infinite number, or not a number, respectively. 110 111 The return value is a pointer to *buffer* with the converted string or 112 ``NULL`` if the conversion failed. The caller is responsible for freeing the 113 returned string by calling :c:func:`PyMem_Free`. 114 115 .. versionadded:: 3.1 116 117 118.. c:function:: int PyOS_stricmp(const char *s1, const char *s2) 119 120 Case insensitive comparison of strings. The function works almost 121 identically to :c:func:`strcmp` except that it ignores the case. 122 123 124.. c:function:: int PyOS_strnicmp(const char *s1, const char *s2, Py_ssize_t size) 125 126 Case insensitive comparison of strings. The function works almost 127 identically to :c:func:`strncmp` except that it ignores the case. 128