typePyFloatObject
This subtype of
represents a Python floating-point object.
PyFloat_Type
Part of the
.This instance of
represents the Python floating-point type. This is the same object as
in the Python layer.
intPyFloat_Check(
*p)
Return true if its argument is a
or a subtype of PyFloatObject. This function always succeeds.
intPyFloat_CheckExact(
*p)
Return true if its argument is a
, but not a subtype of PyFloatObject. This function always succeeds.
*PyFloat_FromString(
*str)
Return value: New reference. Part of the
.Create a
object based on the string value in str, or NULL on failure.
*PyFloat_FromDouble(doublev)
Return value: New reference. Part of the
.Create a
object from v, or NULL on failure.
doublePyFloat_AsDouble(
*pyfloat)
Part of the
.Return a C double representation of the contents of pyfloat. If pyfloat is not a Python floating-point object but has a
method, this method will first be called to convert pyfloat into a float. If __float__() is not defined then it falls back to
. This method returns -1.0 upon failure, so one should call
to check for errors.
Changed in version 3.8: Use
if available.
doublePyFloat_AS_DOUBLE(
*pyfloat)
Return a C double representation of the contents of pyfloat, but without error checking.
*PyFloat_GetInfo(void)
Return value: New reference. Part of the
.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.
doublePyFloat_GetMax()
Part of the
.Return the maximum representable finite float DBL_MAX as C double.
doublePyFloat_GetMin()
Part of the
.Return the minimum normalized positive float DBL_MIN as C double.
Py_INFINITY
This macro expands to a constant expression of type double, that represents the positive infinity.
On most platforms, this is equivalent to the INFINITY macro from the C11 standard <math.h> header.
Py_NAN
This macro expands to a constant expression of type double, that represents a quiet not-a-number (qNaN) value.
On most platforms, this is equivalent to the NAN macro from the C11 standard <math.h> header.
Py_HUGE_VAL
Equivalent to INFINITY.
Py_MATH_E
The definition (accurate for a double type) of the
constant.
Py_MATH_El
High precision (long double) definition of
constant.
Py_MATH_PI
The definition (accurate for a double type) of the
constant.
Py_MATH_PIl
High precision (long double) definition of
constant.
Py_MATH_TAU
The definition (accurate for a double type) of the
constant.
Added in version 3.6.
Py_RETURN_NAN
Return
from a function.
On most platforms, this is equivalent to returnPyFloat_FromDouble(NAN).
Py_RETURN_INF(sign)
Return
or -math.inf from a function, depending on the sign of sign.
On most platforms, this is equivalent to the following:
returnPyFloat_FromDouble(copysign(INFINITY,sign));Py_IS_FINITE(X)
Return 1 if the given floating-point number X is finite, that is, it is normal, subnormal or zero, but not infinite or NaN. Return 0 otherwise.
Deprecated since version 3.14: The macro is
. Use isfinite instead.
Py_IS_INFINITY(X)
Return 1 if the given floating-point number X is positive or negative infinity. Return 0 otherwise.
Deprecated since version 3.14: The macro is
. Use isinf instead.
Py_IS_NAN(X)
Return 1 if the given floating-point number X is a not-a-number (NaN) value. Return 0 otherwise.
Deprecated since version 3.14: The macro is
. Use isnan instead.
Pack and Unpack functions
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.
Note that NaN type may not be preserved on IEEE platforms (signaling NaNs become quiet NaNs), for example on x86 systems in 32-bit mode.
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).
Added in version 3.11.
Pack functions
The pack routines write 2, 4 or 8 bytes, starting at p. le is an int argument, non-zero if you want the bytes string in little-endian format (exponent last, at p+1, p+3, or p+6 and p+7), zero if you want big-endian format (exponent first, at p). The 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
).
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.
intPyFloat_Pack2(doublex, char*p, intle)
Pack a C double as the IEEE 754 binary16 half-precision format.
intPyFloat_Pack4(doublex, char*p, intle)
Pack a C double as the IEEE 754 binary32 single precision format.
intPyFloat_Pack8(doublex, char*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 at p. le is an 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). The 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
is true (and an exception is set, most likely
).
Note that on a non-IEEE platform this will refuse to unpack a bytes string that represents a NaN or infinity.
doublePyFloat_Unpack2(constchar*p, intle)
Unpack the IEEE 754 binary16 half-precision format as a C double.
doublePyFloat_Unpack4(constchar*p, intle)
Unpack the IEEE 754 binary32 single precision format as a C double.
doublePyFloat_Unpack8(constchar*p, intle)
Unpack the IEEE 754 binary64 double precision format as a C double.