42753edb3c
python/m5/smartdict.py:
Add a comment explaining why this actually works.
--HG--
extra : convert_revision : 39cbde547f4bf6cf626ab1c0b6ef56a5788b09b8
109 lines
3.7 KiB
Python
109 lines
3.7 KiB
Python
# The SmartDict class fixes a couple of issues with using the content
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# of os.environ or similar dicts of strings as Python variables:
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#
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# 1) Undefined variables should return False rather than raising KeyError.
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#
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# 2) String values of 'False', '0', etc., should evaluate to False
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# (not just the empty string).
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#
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# #1 is solved by overriding __getitem__, and #2 is solved by using a
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# proxy class for values and overriding __nonzero__ on the proxy.
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# Everything else is just to (a) make proxies behave like normal
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# values otherwise, (b) make sure any dict operation returns a proxy
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# rather than a normal value, and (c) coerce values written to the
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# dict to be strings.
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from convert import *
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class SmartDict(dict):
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class Proxy(str):
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def __int__(self):
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return int(to_integer(str(self)))
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def __long__(self):
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return long(to_integer(str(self)))
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def __float__(self):
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return float(to_integer(str(self)))
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def __nonzero__(self):
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return to_bool(str(self))
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def convert(self, other):
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t = type(other)
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if t == bool:
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return bool(self)
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if t == int:
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return int(self)
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if t == long:
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return long(self)
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if t == float:
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return float(self)
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return str(self)
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def __lt__(self, other):
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return self.convert(other) < other
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def __le__(self, other):
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return self.convert(other) <= other
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def __eq__(self, other):
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return self.convert(other) == other
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def __ne__(self, other):
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return self.convert(other) != other
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def __gt__(self, other):
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return self.convert(other) > other
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def __ge__(self, other):
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return self.convert(other) >= other
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def __add__(self, other):
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return self.convert(other) + other
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def __sub__(self, other):
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return self.convert(other) - other
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def __mul__(self, other):
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return self.convert(other) * other
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def __div__(self, other):
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return self.convert(other) / other
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def __truediv__(self, other):
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return self.convert(other) / other
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def __radd__(self, other):
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return other + self.convert(other)
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def __rsub__(self, other):
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return other - self.convert(other)
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def __rmul__(self, other):
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return other * self.convert(other)
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def __rdiv__(self, other):
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return other / self.convert(other)
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def __rtruediv__(self, other):
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return other / self.convert(other)
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# __getitem__ uses dict.get() to return 'False' if the key is not
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# found (rather than raising KeyError). Note that this does *not*
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# set the key's value to 'False' in the dict, so that even after
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# we call env['foo'] we still get a meaningful answer from "'foo'
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# in env" (which calls dict.__contains__, which we do not
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# override).
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def __getitem__(self, key):
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return self.Proxy(dict.get(self, key, 'False'))
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def __setitem__(self, key, item):
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dict.__setitem__(self, key, str(item))
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def values(self):
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return [ self.Proxy(v) for v in dict.values(self) ]
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def itervalues(self):
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for value in dict.itervalues(self):
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yield self.Proxy(value)
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def items(self):
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return [ (k, self.Proxy(v)) for k,v in dict.items(self) ]
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def iteritems(self):
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for key,value in dict.iteritems(self):
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yield key, self.Proxy(value)
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def get(self, key, default='False'):
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return self.Proxy(dict.get(self, key, str(default)))
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def setdefault(self, key, default='False'):
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return self.Proxy(dict.setdefault(self, key, str(default)))
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