Functions for number conversion and formatted string output.
PyOS_snprintf
(char *str, size_t size, const char *format, ...)PyOS_vsnprintf
(char *str, size_t size, const char *format, va_list va)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:
0 <= rv < size
, the output conversion was successful and rv characters were written to str (excluding the trailing '\0'
byte at str*[*rv]).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.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.
PyOS_string_to_double
(const char *s, char **endptr, PyObject *overflow_exception)Convert a string s
to 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 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
.
New in version 3.1.
PyOS_double_to_string
(double val, char format_code, int precision, int flags, int *ptype)Convert a 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 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 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 PyMem_Free()
.
New in version 3.1.
PyOS_stricmp
(const char *s1, const char *s2)strcmp()
except that it ignores the case.PyOS_strnicmp
(const char *s1, const char *s2, Py_ssize_t size)strncmp()
except that it ignores the case.