[Python-ideas] Exact integral types in struct

Serhiy Storchaka storchaka at gmail.com
Tue Mar 20 21:27:24 CET 2012

20.03.12 21:54, Andrew Svetlov написав(ла):
> Floating points from IEEE 754 doesn't depends from machine byte order
> and C double is always coded in 8 bytes as I know,

Full code:

def _floatconstants():
     _BYTES = binascii.unhexlify(b'7FF80000000000007FF0000000000000')
     if sys.byteorder != 'big':
         _BYTES = _BYTES[:8][::-1] + _BYTES[8:][::-1]
     nan, inf = struct.unpack('dd', _BYTES)
     return nan, inf, -inf

NaN, PosInf, NegInf = _floatconstants()

But in xdrlib.py:

         return struct.unpack('>d', data)[0]

And in pickle.py:

         self.append(unpack('>d', self.read(8))[0])


  >>> import struct
  >>> struct.pack('>d', 1)
  >>> struct.pack('<d', 1)

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