浮點數（Floating-Point）物件

typePyFloatObject

This subtype ofPyObject represents a Python floating-point object.

PyTypeObjectPyFloat_Type
為穩定 ABI 的一部分.

This instance ofPyTypeObject represents the Python floating-pointtype. This is the same object asfloat in the Python layer.

intPyFloat_Check(PyObject*p)

Return true if its argument is aPyFloatObject or a subtype ofPyFloatObject. This function always succeeds.

intPyFloat_CheckExact(PyObject*p)

Return true if its argument is aPyFloatObject, but not a subtype ofPyFloatObject. This function always succeeds.

PyObject*PyFloat_FromString(PyObject*str)
回傳值：新的參照。 為穩定 ABI 的一部分.

Create aPyFloatObject object based on the string value instr, orNULL on failure.

PyObject*PyFloat_FromDouble(doublev)
回傳值：新的參照。 為穩定 ABI 的一部分.

Create aPyFloatObject object fromv, orNULL on failure.

doublePyFloat_AsDouble(PyObject*pyfloat)
為穩定 ABI 的一部分.

Return a Cdouble representation of the contents ofpyfloat. Ifpyfloat is not a Python floating-point object but has a__float__()method, this method will first be called to convertpyfloat into a float.If__float__() is not defined then it falls back to__index__().This method returns-1.0 upon failure, so one should callPyErr_Occurred() to check for errors.

在 3.8 版的變更:Use__index__() if available.

doublePyFloat_AS_DOUBLE(PyObject*pyfloat)

Return a Cdouble representation of the contents ofpyfloat, butwithout error checking.

PyObject*PyFloat_GetInfo(void)
回傳值：新的參照。 為穩定 ABI 的一部分.

Return a structseq instance which contains information about theprecision, minimum and maximum values of a float. It's a thin wrapperaround the header filefloat.h.

doublePyFloat_GetMax()
為穩定 ABI 的一部分.

Return the maximum representable finite floatDBL_MAX as Cdouble.

doublePyFloat_GetMin()
為穩定 ABI 的一部分.

Return the minimum normalized positive floatDBL_MIN as Cdouble.

Pack and Unpack functions

The pack and unpack functions provide an efficient platform-independent way tostore floating-point values as byte strings. The Pack routines produce a bytesstring from a Cdouble, and the Unpack routines produce a Cdouble from such a bytes string. The suffix (2, 4 or 8) specifies thenumber of bytes in the bytes string.

On platforms that appear to use IEEE 754 formats these functions work bycopying bits. On other platforms, the 2-byte format is identical to the IEEE754 binary16 half-precision format, the 4-byte format (32-bit) is identical tothe IEEE 754 binary32 single precision format, and the 8-byte format to theIEEE 754 binary64 double precision format, although the packing of INFs andNaNs (if such things exist on the platform) isn't handled correctly, andattempting to unpack a bytes string containing an IEEE INF or NaN will raise anexception.

On non-IEEE platforms with more precision, or larger dynamic range, than IEEE754 supports, not all values can be packed; on non-IEEE platforms with lessprecision, or smaller dynamic range, not all values can be unpacked. Whathappens in such cases is partly accidental (alas).

在 3.11 版被加入.

Pack functions

The pack routines write 2, 4 or 8 bytes, starting atp.le is anint argument, non-zero if you want the bytes string in little-endianformat (exponent last, atp+1,p+3, orp+6p+7), zero if youwant big-endian format (exponent first, atp). ThePY_BIG_ENDIANconstant can be used to use the native endian: it is equal to1 on bigendian processor, or0 on little endian processor.

Return value:0 if all is OK,-1 if error (and an exception is set,most likelyOverflowError).

There are two problems on non-IEEE platforms:

  • What this does is undefined ifx is a NaN or infinity.

  • -0.0 和+0.0 會產生同樣的位元組字串。

intPyFloat_Pack2(doublex,unsignedchar*p,intle)

Pack a C double as the IEEE 754 binary16 half-precision format.

intPyFloat_Pack4(doublex,unsignedchar*p,intle)

Pack a C double as the IEEE 754 binary32 single precision format.

intPyFloat_Pack8(doublex,unsignedchar*p,intle)

Pack a C double as the IEEE 754 binary64 double precision format.

Unpack functions

The unpack routines read 2, 4 or 8 bytes, starting atp.le is anint argument, non-zero if the bytes string is in little-endian format(exponent last, atp+1,p+3 orp+6 andp+7), zero if big-endian(exponent first, atp). ThePY_BIG_ENDIAN constant can be used touse the native endian: it is equal to1 on big endian processor, or0on little endian processor.

Return value: The unpacked double. On error, this is-1.0 andPyErr_Occurred() is true (and an exception is set, most likelyOverflowError).

Note that on a non-IEEE platform this will refuse to unpack a bytes string thatrepresents a NaN or infinity.

doublePyFloat_Unpack2(constunsignedchar*p,intle)

Unpack the IEEE 754 binary16 half-precision format as a C double.

doublePyFloat_Unpack4(constunsignedchar*p,intle)

Unpack the IEEE 754 binary32 single precision format as a C double.

doublePyFloat_Unpack8(constunsignedchar*p,intle)

Unpack the IEEE 754 binary64 double precision format as a C double.