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# The SmartDict class fixes a couple of issues with using the content
# of os.environ or similar dicts of strings as Python variables:
#
# 1) Undefined variables should return False rather than raising KeyError.
#
# 2) String values of 'False', '0', etc., should evaluate to False
# (not just the empty string).
#
# #1 is solved by overriding __getitem__, and #2 is solved by using a
# proxy class for values and overriding __nonzero__ on the proxy.
# Everything else is just to (a) make proxies behave like normal
# values otherwise, (b) make sure any dict operation returns a proxy
# rather than a normal value, and (c) coerce values written to the
# dict to be strings.
from convert import *
class Variable(str):
"""Intelligent proxy class for SmartDict. Variable will use the
various convert functions to attempt to convert values to useable
types"""
def __int__(self):
return toInteger(str(self))
def __long__(self):
return toLong(str(self))
def __float__(self):
return toFloat(str(self))
def __nonzero__(self):
return toBool(str(self))
def convert(self, other):
t = type(other)
if t == bool:
return bool(self)
if t == int:
return int(self)
if t == long:
return long(self)
if t == float:
return float(self)
return str(self)
def __lt__(self, other):
return self.convert(other) < other
def __le__(self, other):
return self.convert(other) <= other
def __eq__(self, other):
return self.convert(other) == other
def __ne__(self, other):
return self.convert(other) != other
def __gt__(self, other):
return self.convert(other) > other
def __ge__(self, other):
return self.convert(other) >= other
def __add__(self, other):
return self.convert(other) + other
def __sub__(self, other):
return self.convert(other) - other
def __mul__(self, other):
return self.convert(other) * other
def __div__(self, other):
return self.convert(other) / other
def __truediv__(self, other):
return self.convert(other) / other
def __radd__(self, other):
return other + self.convert(other)
def __rsub__(self, other):
return other - self.convert(other)
def __rmul__(self, other):
return other * self.convert(other)
def __rdiv__(self, other):
return other / self.convert(other)
def __rtruediv__(self, other):
return other / self.convert(other)
class UndefinedVariable(object):
"""Placeholder class to represent undefined variables. Will
generally cause an exception whenever it is used, but evaluates to
zero for boolean truth testing such as in an if statement"""
def __nonzero__(self):
return False
class SmartDict(dict):
"""Dictionary class that holds strings, but intelligently converts
those strings to other types depending on their usage"""
def __getitem__(self, key):
"""returns a Variable proxy if the values exists in the database and
returns an UndefinedVariable otherwise"""
if key in self:
return Variable(dict.get(self, key))
else:
# Note that this does *not* change the contents of the dict,
# so that even after we call env['foo'] we still get a
# meaningful answer from "'foo' in env" (which
# calls dict.__contains__, which we do not override).
return UndefinedVariable()
def __setitem__(self, key, item):
"""intercept the setting of any variable so that we always
store strings in the dict"""
dict.__setitem__(self, key, str(item))
def values(self):
return [ Variable(v) for v in dict.values(self) ]
def itervalues(self):
for value in dict.itervalues(self):
yield Variable(value)
def items(self):
return [ (k, Variable(v)) for k,v in dict.items(self) ]
def iteritems(self):
for key,value in dict.iteritems(self):
yield key, Variable(value)
def get(self, key, default='False'):
return Variable(dict.get(self, key, str(default)))
def setdefault(self, key, default='False'):
return Variable(dict.setdefault(self, key, str(default)))
__all__ = [ 'SmartDict' ]
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