此实例的
PyTypeObject
represents the Python floating point type. This is the same object as
float
在 Python 层。
返回 True 若其自变量是
PyFloatObject
或子类型的
PyFloatObject
. This function always succeeds.
返回 True 若其自变量是
PyFloatObject
，但不是子类型的
PyFloatObject
. This function always succeeds.
创建
PyFloatObject
object based on the string value in
str
，或
NULL
当故障时。
创建
PyFloatObject
对象从
v
，或
NULL
当故障时。
返回 C
double
representation of the contents of
pyfloat
。若
pyfloat
is not a Python floating point object but has a
__float__()
method, this method will first be called to convert
pyfloat
into a float. If
__float__()
is not defined then it falls back to
__index__()
。此方法返回
-1.0
upon failure, so one should call
PyErr_Occurred()
to check for errors.
3.8 版改变：
使用
__index__()
if available.
返回 C double representation of the contents of pyfloat , but without error checking.
Return a structseq instance which contains information about the precision, minimum and maximum values of a float. It’s a thin wrapper around the header file
float.h
.
Return the maximum representable finite float DBL_MAX as C double .
Return the minimum normalized positive float DBL_MIN as C double .
The pack and unpack functions provide an efficient platform-independent way to store floating-point values as byte strings. The Pack routines produce a bytes string from a C double , and the Unpack routines produce a C double from such a bytes string. The suffix (2, 4 or 8) specifies the number of bytes in the bytes string.
On platforms that appear to use IEEE 754 formats these functions work by copying bits. On other platforms, the 2-byte format is identical to the IEEE 754 binary16 half-precision format, the 4-byte format (32-bit) is identical to the IEEE 754 binary32 single precision format, and the 8-byte format to the IEEE 754 binary64 double precision format, although the packing of INFs and NaNs (if such things exist on the platform) isn’t handled correctly, and attempting to unpack a bytes string containing an IEEE INF or NaN will raise an exception.
On non-IEEE platforms with more precision, or larger dynamic range, than IEEE 754 supports, not all values can be packed; on non-IEEE platforms with less precision, or smaller dynamic range, not all values can be unpacked. What happens in such cases is partly accidental (alas).
3.11 版新增。
The pack routines write 2, 4 or 8 bytes, starting at
p
.
le
是
int
argument, non-zero if you want the bytes string in little-endian format (exponent last, at
p+1
,
p+3
，或
p+6
p+7
), zero if you want big-endian format (exponent first, at
p
)。
PY_BIG_ENDIAN
constant can be used to use the native endian: it is equal to
1
on big endian processor, or
0
on little endian processor.
Return value:
0
if all is OK,
-1
if error (and an exception is set, most likely
OverflowError
).
There are two problems on non-IEEE platforms:
What this does is undefined if x is a NaN or infinity.
-0.0
and
+0.0
produce the same bytes string.
Pack a C double as the IEEE 754 binary16 half-precision format.
Pack a C double as the IEEE 754 binary32 single precision format.
Pack a C double as the IEEE 754 binary64 double precision format.
The unpack routines read 2, 4 or 8 bytes, starting at
p
.
le
是
int
argument, non-zero if the bytes string is in little-endian format (exponent last, at
p+1
,
p+3
or
p+6
and
p+7
), zero if big-endian (exponent first, at
p
)。
PY_BIG_ENDIAN
constant can be used to use the native endian: it is equal to
1
on big endian processor, or
0
on little endian processor.
Return value: The unpacked double. On error, this is
-1.0
and
PyErr_Occurred()
is true (and an exception is set, most likely
OverflowError
).
Note that on a non-IEEE platform this will refuse to unpack a bytes string that represents a NaN or infinity.
Unpack the IEEE 754 binary16 half-precision format as a C double.
Unpack the IEEE 754 binary32 single precision format as a C double.
Unpack the IEEE 754 binary64 double precision format as a C double.
