字符串转换和格式化 ¶

Functions for number conversion and formatted string output.

int PyOS_snprintf ( char * str , size_t size , const char * format , ... ) ¶: 属于稳定 ABI (应用程序二进制接口) .
Output not more than size bytes to str according to the format string format and the extra arguments. See the Unix man page snprintf(3) .

int PyOS_vsnprintf ( char * str , size_t size , const char * format , va_list va ) ¶: 属于稳定 ABI (应用程序二进制接口) .
Output not more than size bytes to str according to the format string format and the variable argument list va . Unix man page vsnprintf(3) .

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 , format != NULL and size < INT_MAX . Note that this means there is no equivalent to the C99 n = snprintf(NULL, 0, ...) which would determine the necessary buffer size.

The return value ( rv ) for these functions should be interpreted as follows:

当 0 <= rv < size , the output conversion was successful and rv characters were written to str (excluding the trailing '\0' byte at str[rv] ).
当 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' 在此情况下。
当 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.

unsigned long PyOS_strtoul ( const char * str , char * * ptr , int base ) ¶

属于稳定 ABI (应用程序二进制接口) .

Convert the initial part of the string in str to an unsigned long value according to the given base , which must be between 2 and 36 inclusive, or be the special value 0 .

Leading white space and case of characters are ignored. If base is zero it looks for a leading 0b , 0o or 0x to tell which base. If these are absent it defaults to 10 . Base must be 0 or between 2 and 36 (inclusive). If ptr 为非 NULL it will contain a pointer to the end of the scan.

If the converted value falls out of range of corresponding return type, range error occurs ( errno 被设为 ERANGE ) 和 ULONG_MAX is returned. If no conversion can be performed, 0 被返回。

See also the Unix man page strtoul(3) .

Added in version 3.2.

long PyOS_strtol ( const char * str , char * * ptr , int base ) ¶

属于稳定 ABI (应用程序二进制接口) .

Convert the initial part of the string in str to an long value according to the given base , which must be between 2 and 36 inclusive, or be the special value 0 .

如同 PyOS_strtoul() , but return a long value instead and LONG_MAX on overflows.

See also the Unix man page strtol(3) .

Added in version 3.2.

double PyOS_string_to_double ( const char * s , char * * endptr , PyObject * overflow_exception ) ¶

属于稳定 ABI (应用程序二进制接口) .

Convert a string s 到 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 s must not have leading or trailing whitespace. The conversion is independent of the current locale.

若 endptr is NULL , convert the whole string. Raise ValueError 并返回 -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 .

若 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 .

Added in version 3.1.

char * PyOS_double_to_string ( double val , char format_code , int precision , int flags , int * ptype ) ¶

属于稳定 ABI (应用程序二进制接口) .

转换 double val to a string using supplied format_code , precision ，和 flags .

format_code must be one of 'e' , 'E' , 'f' , 'F' , 'g' , 'G' or 'r' 。对于 'r' , the supplied precision must be 0 and is ignored. The 'r' format code specifies the standard repr() 格式。

flags can be zero or more of the values Py_DTSF_SIGN , Py_DTSF_ADD_DOT_0 ，或 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 PyOS_snprintf() '#' specifier for details.

若 ptype 为非 NULL , then the value it points to will be set to one of Py_DTST_FINITE , Py_DTST_INFINITE ，或 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 PyMem_Free() .

Added in version 3.1.

int PyOS_stricmp ( const char * s1 , const char * s2 ) ¶

int PyOS_strnicmp ( const char * s1 , const char * s2 , Py_ssize_t size ) ¶

字符串转换和格式化 ¶

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