String conversion and formatting¶
Functions for number conversion and formatted string output.
- 
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 snprintf(2). 
- 
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 vsnprintf(2). 
PyOS_snprintf() and PyOS_vsnprintf() wrap the Standard C library
functions snprintf() and 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 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 + 1bytes 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.
- 
double PyOS_string_to_double(const char *s, char **endptr, PyObject *overflow_exception)¶
- Convert a string - sto a- double, raising a Python exception on failure. The set of accepted strings corresponds to the set of strings accepted by Python’s- float()constructor, except that- smust not have leading or trailing whitespace. The conversion is independent of the current locale.- If - endptris- NULL, convert the whole string. Raise- ValueErrorand return- -1.0if 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- *endptrto point to the first unconverted character. If no initial segment of the string is the valid representation of a floating-point number, set- *endptrto point to the beginning of the string, raise ValueError, and return- -1.0.- If - srepresents a value that is too large to store in a float (for example,- "1e500"is such a string on many platforms) then if- overflow_exceptionis- NULLreturn- Py_HUGE_VAL(with an appropriate sign) and don’t set any exception. Otherwise,- overflow_exceptionmust point to a Python exception object; raise that exception and return- -1.0. In both cases, set- *endptrto 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.- New in version 3.1. 
- 
char* PyOS_double_to_string(double val, char format_code, int precision, int flags, int *ptype)¶
- Convert a - doubleval 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- 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_SIGNmeans to always precede the returned string with a sign character, even if val is non-negative.
- Py_DTSF_ADD_DOT_0means to ensure that the returned string will not look like an integer.
- Py_DTSF_ALTmeans to apply “alternate” formatting rules. See the documentation for the- 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 - NULLif the conversion failed. The caller is responsible for freeing the returned string by calling- PyMem_Free().- New in version 3.1. 
- 
int PyOS_stricmp(const char *s1, const char *s2)¶
- Case insensitive comparison of strings. The function works almost identically to - strcmp()except that it ignores the case.
- 
int PyOS_strnicmp(const char *s1, const char *s2, Py_ssize_t size)¶
- Case insensitive comparison of strings. The function works almost identically to - strncmp()except that it ignores the case.
