I'm working with the following code. I included some tests to make it
easy to see--if you run the code--what troubles I'm having.
Can some one *please* splain me why str(obj) works but not print obj,
and why obj.__int__() works, but not int(obj). I just don't get it. :(
BTW: The reason I'm going to all this mess is that I need a Byte object
that can
* print like a byte e.g. \x00
* adds like a string (concatinates)
* does bitwise math like a byte
* coereces to an int
* works with ''.join() -- The whole reason I'm inheriting from str
* Oh yeah, and some other classes inherit from it and have sequence
like behavior
Much thanks to any that can unveil the mystery and correct my broken
understanding.
regards
--
mthorley
<code>
import struct
class Byte(str): # Implement Bytes as str for easy adding and joining
"""Byte data type
Inherits from str so join will work, but supports bitwise
operations
via operator overloading. Given a digit it uses struct to
produce
the correct string format. Given a non digit string, it
attempts to
convert it to a digit using struct.unpack, and initialize its
self
>>> b = Byte(1)
>>> b
'\\x01'
>>> str(b)
'\\x01'
>>> b + b
'\\x01\\x01'
>>> ''.join([b,b])
'\\x01\\x01'
>>> b[0]
'\\x01'
>>> for i in b: i
'\\x01'
>>> b >> 8
0
>>> b << 8
256
>>> b._int
1
>>> len(b)
1
>>> type(b._int)
<type 'int'>
>>> b.__int__()
1
>>> int(b)
1
>>> print b
1
"""
def __new__(self, val):
if type(val) == str and not val.isdigit():
val = struct.unpack('B', val) #ensure input is valid struct
byte
self._byte = struct.pack('B', val)
self._int = int(val)
return str.__new__(self, self._byte)
def __int__(self):
return self._int
def __lshift__(self, x):
return self._int << x
def __rshift__(self, x):
return self._int >> x
def __len__(self):
return 1
def _test():
import doctest
doctest.testmod()
if __name__ == '__main__':
_test()
</code>
--
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