Functions for number conversion and formatted string output.
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(3) .
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(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
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:
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'
在这种情况下。
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.
PyOS_string_to_double
(
const char
*s
, char
**endptr
,
PyObject
*overflow_exception
)
¶
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
.
3.1 版新增。
PyOS_double_to_string
(
double
val
, char
format_code
, int
precision
, int
flags
, int
*ptype
)
¶
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'
. For
'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()
.
3.1 版新增。
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.
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.