smartdict.py revision 6997:5af4976c17e2
1# Copyright (c) 2005 The Regents of The University of Michigan 2# All rights reserved. 3# 4# Redistribution and use in source and binary forms, with or without 5# modification, are permitted provided that the following conditions are 6# met: redistributions of source code must retain the above copyright 7# notice, this list of conditions and the following disclaimer; 8# redistributions in binary form must reproduce the above copyright 9# notice, this list of conditions and the following disclaimer in the 10# documentation and/or other materials provided with the distribution; 11# neither the name of the copyright holders nor the names of its 12# contributors may be used to endorse or promote products derived from 13# this software without specific prior written permission. 14# 15# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 18# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 19# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 20# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 21# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 25# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26# 27# Authors: Nathan Binkert 28 29# The SmartDict class fixes a couple of issues with using the content 30# of os.environ or similar dicts of strings as Python variables: 31# 32# 1) Undefined variables should return False rather than raising KeyError. 33# 34# 2) String values of 'False', '0', etc., should evaluate to False 35# (not just the empty string). 36# 37# #1 is solved by overriding __getitem__, and #2 is solved by using a 38# proxy class for values and overriding __nonzero__ on the proxy. 39# Everything else is just to (a) make proxies behave like normal 40# values otherwise, (b) make sure any dict operation returns a proxy 41# rather than a normal value, and (c) coerce values written to the 42# dict to be strings. 43 44 45from convert import * 46from attrdict import attrdict 47 48class Variable(str): 49 """Intelligent proxy class for SmartDict. Variable will use the 50 various convert functions to attempt to convert values to useable 51 types""" 52 def __int__(self): 53 return toInteger(str(self)) 54 def __long__(self): 55 return toLong(str(self)) 56 def __float__(self): 57 return toFloat(str(self)) 58 def __nonzero__(self): 59 return toBool(str(self)) 60 def convert(self, other): 61 t = type(other) 62 if t == bool: 63 return bool(self) 64 if t == int: 65 return int(self) 66 if t == long: 67 return long(self) 68 if t == float: 69 return float(self) 70 return str(self) 71 def __lt__(self, other): 72 return self.convert(other) < other 73 def __le__(self, other): 74 return self.convert(other) <= other 75 def __eq__(self, other): 76 return self.convert(other) == other 77 def __ne__(self, other): 78 return self.convert(other) != other 79 def __gt__(self, other): 80 return self.convert(other) > other 81 def __ge__(self, other): 82 return self.convert(other) >= other 83 84 def __add__(self, other): 85 return self.convert(other) + other 86 def __sub__(self, other): 87 return self.convert(other) - other 88 def __mul__(self, other): 89 return self.convert(other) * other 90 def __div__(self, other): 91 return self.convert(other) / other 92 def __truediv__(self, other): 93 return self.convert(other) / other 94 95 def __radd__(self, other): 96 return other + self.convert(other) 97 def __rsub__(self, other): 98 return other - self.convert(other) 99 def __rmul__(self, other): 100 return other * self.convert(other) 101 def __rdiv__(self, other): 102 return other / self.convert(other) 103 def __rtruediv__(self, other): 104 return other / self.convert(other) 105 106class UndefinedVariable(object): 107 """Placeholder class to represent undefined variables. Will 108 generally cause an exception whenever it is used, but evaluates to 109 zero for boolean truth testing such as in an if statement""" 110 def __nonzero__(self): 111 return False 112 113class SmartDict(attrdict): 114 """Dictionary class that holds strings, but intelligently converts 115 those strings to other types depending on their usage""" 116 117 def __getitem__(self, key): 118 """returns a Variable proxy if the values exists in the database and 119 returns an UndefinedVariable otherwise""" 120 121 if key in self: 122 return Variable(dict.get(self, key)) 123 else: 124 # Note that this does *not* change the contents of the dict, 125 # so that even after we call env['foo'] we still get a 126 # meaningful answer from "'foo' in env" (which 127 # calls dict.__contains__, which we do not override). 128 return UndefinedVariable() 129 130 def __setitem__(self, key, item): 131 """intercept the setting of any variable so that we always 132 store strings in the dict""" 133 dict.__setitem__(self, key, str(item)) 134 135 def values(self): 136 return [ Variable(v) for v in dict.values(self) ] 137 138 def itervalues(self): 139 for value in dict.itervalues(self): 140 yield Variable(value) 141 142 def items(self): 143 return [ (k, Variable(v)) for k,v in dict.items(self) ] 144 145 def iteritems(self): 146 for key,value in dict.iteritems(self): 147 yield key, Variable(value) 148 149 def get(self, key, default='False'): 150 return Variable(dict.get(self, key, str(default))) 151 152 def setdefault(self, key, default='False'): 153 return Variable(dict.setdefault(self, key, str(default))) 154 155__all__ = [ 'SmartDict' ] 156