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1 | 1 | # -*- coding: utf-8 -*- |
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2 | 2 | """Mimic C structs with lots of extra functionality. |
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3 | 3 | |
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4 |
$Id: ipstruct.py 19 |
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4 | $Id: ipstruct.py 1950 2006-11-28 19:15:35Z vivainio $""" | |
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5 | 5 | |
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6 | 6 | #***************************************************************************** |
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7 | 7 | # Copyright (C) 2001-2004 Fernando Perez <fperez@colorado.edu> |
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8 | 8 | # |
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9 | 9 | # Distributed under the terms of the BSD License. The full license is in |
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10 | 10 | # the file COPYING, distributed as part of this software. |
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11 | 11 | #***************************************************************************** |
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12 | 12 | |
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13 | 13 | from IPython import Release |
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14 | 14 | __author__ = '%s <%s>' % Release.authors['Fernando'] |
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15 | 15 | __license__ = Release.license |
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16 | 16 | |
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17 | 17 | __all__ = ['Struct'] |
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18 | 18 | |
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19 | 19 | import types |
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20 | import pprint | |
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20 | 21 | |
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21 | 22 | from IPython.genutils import list2dict2 |
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22 | 23 | |
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23 | 24 | class Struct: |
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24 | 25 | """Class to mimic C structs but also provide convenient dictionary-like |
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25 | 26 | functionality. |
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26 | 27 | |
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27 | 28 | Instances can be initialized with a dictionary, a list of key=value pairs |
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28 | 29 | or both. If both are present, the dictionary must come first. |
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29 | 30 | |
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30 | 31 | Because Python classes provide direct assignment to their members, it's |
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31 | 32 | easy to overwrite normal methods (S.copy = 1 would destroy access to |
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32 | 33 | S.copy()). For this reason, all builtin method names are protected and |
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33 | 34 | can't be assigned to. An attempt to do s.copy=1 or s['copy']=1 will raise |
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34 | 35 | a KeyError exception. If you really want to, you can bypass this |
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35 | 36 | protection by directly assigning to __dict__: s.__dict__['copy']=1 will |
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36 | 37 | still work. Doing this will break functionality, though. As in most of |
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37 | 38 | Python, namespace protection is weakly enforced, so feel free to shoot |
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38 | 39 | yourself if you really want to. |
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39 | 40 | |
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40 | 41 | Note that this class uses more memory and is *much* slower than a regular |
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41 | 42 | dictionary, so be careful in situations where memory or performance are |
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42 | 43 | critical. But for day to day use it should behave fine. It is particularly |
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43 | 44 | convenient for storing configuration data in programs. |
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44 | 45 | |
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45 | 46 | +,+=,- and -= are implemented. +/+= do merges (non-destructive updates), |
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46 | 47 | -/-= remove keys from the original. See the method descripitions. |
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47 | 48 | |
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48 | 49 | This class allows a quick access syntax: both s.key and s['key'] are |
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49 | 50 | valid. This syntax has a limitation: each 'key' has to be explicitly |
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50 | 51 | accessed by its original name. The normal s.key syntax doesn't provide |
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51 | 52 | access to the keys via variables whose values evaluate to the desired |
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52 | 53 | keys. An example should clarify this: |
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53 | 54 | |
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54 | 55 | Define a dictionary and initialize both with dict and k=v pairs: |
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55 | 56 | >>> d={'a':1,'b':2} |
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56 | 57 | >>> s=Struct(d,hi=10,ho=20) |
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57 | 58 | The return of __repr__ can be used to create a new instance: |
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58 | 59 | >>> s |
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59 | 60 | Struct({'ho': 20, 'b': 2, 'hi': 10, 'a': 1}) |
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60 | 61 | __str__ (called by print) shows it's not quite a regular dictionary: |
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61 | 62 | >>> print s |
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62 | 63 | Struct {a: 1, b: 2, hi: 10, ho: 20} |
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63 | 64 | Access by explicitly named key with dot notation: |
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64 | 65 | >>> s.a |
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65 | 66 | 1 |
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66 | 67 | Or like a dictionary: |
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67 | 68 | >>> s['a'] |
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68 | 69 | 1 |
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69 | 70 | If you want a variable to hold the key value, only dictionary access works: |
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70 | 71 | >>> key='hi' |
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71 | 72 | >>> s.key |
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72 | 73 | Traceback (most recent call last): |
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73 | 74 | File "<stdin>", line 1, in ? |
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74 | 75 | AttributeError: Struct instance has no attribute 'key' |
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75 | 76 | >>> s[key] |
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76 | 77 | 10 |
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77 | 78 | |
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78 | 79 | Another limitation of the s.key syntax (and Struct(key=val) |
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79 | 80 | initialization): keys can't be numbers. But numeric keys can be used and |
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80 | 81 | accessed using the dictionary syntax. Again, an example: |
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81 | 82 | |
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82 | 83 | This doesn't work: |
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83 | 84 | >>> s=Struct(4='hi') |
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84 | 85 | SyntaxError: keyword can't be an expression |
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85 | 86 | But this does: |
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86 | 87 | >>> s=Struct() |
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87 | 88 | >>> s[4]='hi' |
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88 | 89 | >>> s |
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89 | 90 | Struct({4: 'hi'}) |
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90 | 91 | >>> s[4] |
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91 | 92 | 'hi' |
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92 | 93 | """ |
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93 | 94 | |
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94 | 95 | # Attributes to which __setitem__ and __setattr__ will block access. |
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95 | 96 | # Note: much of this will be moot in Python 2.2 and will be done in a much |
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96 | 97 | # cleaner way. |
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97 | 98 | __protected = ('copy dict dictcopy get has_attr has_key items keys ' |
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98 | 99 | 'merge popitem setdefault update values ' |
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99 | 100 | '__make_dict __dict_invert ').split() |
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100 | 101 | |
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101 | 102 | def __init__(self,dict=None,**kw): |
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102 | 103 | """Initialize with a dictionary, another Struct, or by giving |
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103 | 104 | explicitly the list of attributes. |
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104 | 105 | |
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105 | 106 | Both can be used, but the dictionary must come first: |
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106 | 107 | Struct(dict), Struct(k1=v1,k2=v2) or Struct(dict,k1=v1,k2=v2). |
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107 | 108 | """ |
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108 | 109 | self.__dict__['__allownew'] = True |
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109 | 110 | if dict is None: |
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110 | 111 | dict = {} |
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111 | 112 | if isinstance(dict,Struct): |
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112 | 113 | dict = dict.dict() |
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113 | 114 | elif dict and type(dict) is not types.DictType: |
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114 | 115 | raise TypeError,\ |
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115 | 116 | 'Initialize with a dictionary or key=val pairs.' |
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116 | 117 | dict.update(kw) |
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117 | 118 | # do the updating by hand to guarantee that we go through the |
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118 | 119 | # safety-checked __setitem__ |
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119 | 120 | for k,v in dict.items(): |
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120 | 121 | self[k] = v |
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121 | 122 | |
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122 | 123 | |
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123 | 124 | def __setitem__(self,key,value): |
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124 | 125 | """Used when struct[key] = val calls are made.""" |
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125 | 126 | if key in Struct.__protected: |
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126 | 127 | raise KeyError,'Key '+`key`+' is a protected key of class Struct.' |
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127 | 128 | if not self['__allownew'] and key not in self.__dict__: |
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128 | 129 | raise KeyError( |
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129 | 130 | "Can't create unknown attribute %s - Check for typos, or use allow_new_attr to create new attributes!" % |
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130 | 131 | key) |
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131 | 132 | |
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132 | 133 | self.__dict__[key] = value |
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133 | 134 | |
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134 | 135 | def __setattr__(self, key, value): |
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135 | 136 | """Used when struct.key = val calls are made.""" |
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136 | 137 | self.__setitem__(key,value) |
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137 | 138 | |
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138 | 139 | def __str__(self): |
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139 | 140 | """Gets called by print.""" |
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140 | 141 | |
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141 |
return 'Struct('+ |
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142 | return 'Struct('+ pprint.pformat(self.__dict__)+')' | |
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142 | 143 | |
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143 | 144 | def __repr__(self): |
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144 | 145 | """Gets called by repr. |
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145 | 146 | |
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146 | 147 | A Struct can be recreated with S_new=eval(repr(S_old)).""" |
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147 |
return |
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148 | return self.__str__() | |
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148 | 149 | |
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149 | 150 | def __getitem__(self,key): |
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150 | 151 | """Allows struct[key] access.""" |
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151 | 152 | return self.__dict__[key] |
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152 | 153 | |
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153 | 154 | def __contains__(self,key): |
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154 | 155 | """Allows use of the 'in' operator.""" |
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155 | 156 | return self.__dict__.has_key(key) |
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156 | 157 | |
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157 | 158 | def __iadd__(self,other): |
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158 | 159 | """S += S2 is a shorthand for S.merge(S2).""" |
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159 | 160 | self.merge(other) |
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160 | 161 | return self |
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161 | 162 | |
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162 | 163 | def __add__(self,other): |
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163 | 164 | """S + S2 -> New Struct made form S and S.merge(S2)""" |
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164 | 165 | Sout = self.copy() |
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165 | 166 | Sout.merge(other) |
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166 | 167 | return Sout |
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167 | 168 | |
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168 | 169 | def __sub__(self,other): |
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169 | 170 | """Return S1-S2, where all keys in S2 have been deleted (if present) |
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170 | 171 | from S1.""" |
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171 | 172 | Sout = self.copy() |
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172 | 173 | Sout -= other |
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173 | 174 | return Sout |
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174 | 175 | |
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175 | 176 | def __isub__(self,other): |
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176 | 177 | """Do in place S = S - S2, meaning all keys in S2 have been deleted |
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177 | 178 | (if present) from S1.""" |
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178 | 179 | |
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179 | 180 | for k in other.keys(): |
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180 | 181 | if self.has_key(k): |
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181 | 182 | del self.__dict__[k] |
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182 | 183 | |
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183 | 184 | def __make_dict(self,__loc_data__,**kw): |
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184 | 185 | "Helper function for update and merge. Return a dict from data." |
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185 | 186 | |
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186 | 187 | if __loc_data__ == None: |
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187 | 188 | dict = {} |
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188 | 189 | elif type(__loc_data__) is types.DictType: |
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189 | 190 | dict = __loc_data__ |
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190 | 191 | elif isinstance(__loc_data__,Struct): |
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191 | 192 | dict = __loc_data__.__dict__ |
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192 | 193 | else: |
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193 | 194 | raise TypeError, 'Update with a dict, a Struct or key=val pairs.' |
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194 | 195 | if kw: |
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195 | 196 | dict.update(kw) |
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196 | 197 | return dict |
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197 | 198 | |
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198 | 199 | def __dict_invert(self,dict): |
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199 | 200 | """Helper function for merge. Takes a dictionary whose values are |
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200 | 201 | lists and returns a dict. with the elements of each list as keys and |
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201 | 202 | the original keys as values.""" |
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202 | 203 | |
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203 | 204 | outdict = {} |
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204 | 205 | for k,lst in dict.items(): |
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205 | 206 | if type(lst) is types.StringType: |
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206 | 207 | lst = lst.split() |
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207 | 208 | for entry in lst: |
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208 | 209 | outdict[entry] = k |
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209 | 210 | return outdict |
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210 | 211 | |
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211 | 212 | def clear(self): |
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212 | 213 | """Clear all attributes.""" |
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213 | 214 | self.__dict__.clear() |
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214 | 215 | |
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215 | 216 | def copy(self): |
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216 | 217 | """Return a (shallow) copy of a Struct.""" |
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217 | 218 | return Struct(self.__dict__.copy()) |
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218 | 219 | |
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219 | 220 | def dict(self): |
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220 | 221 | """Return the Struct's dictionary.""" |
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221 | 222 | return self.__dict__ |
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222 | 223 | |
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223 | 224 | def dictcopy(self): |
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224 | 225 | """Return a (shallow) copy of the Struct's dictionary.""" |
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225 | 226 | return self.__dict__.copy() |
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226 | 227 | |
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227 | 228 | def popitem(self): |
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228 | 229 | """S.popitem() -> (k, v), remove and return some (key, value) pair as |
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229 | 230 | a 2-tuple; but raise KeyError if S is empty.""" |
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230 | 231 | return self.__dict__.popitem() |
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231 | 232 | |
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232 | 233 | def update(self,__loc_data__=None,**kw): |
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233 | 234 | """Update (merge) with data from another Struct or from a dictionary. |
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234 | 235 | Optionally, one or more key=value pairs can be given at the end for |
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235 | 236 | direct update.""" |
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236 | 237 | |
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237 | 238 | # The funny name __loc_data__ is to prevent a common variable name which |
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238 | 239 | # could be a fieled of a Struct to collide with this parameter. The problem |
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239 | 240 | # would arise if the function is called with a keyword with this same name |
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240 | 241 | # that a user means to add as a Struct field. |
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241 | 242 | newdict = Struct.__make_dict(self,__loc_data__,**kw) |
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242 | 243 | for k,v in newdict.items(): |
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243 | 244 | self[k] = v |
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244 | 245 | |
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245 | 246 | def merge(self,__loc_data__=None,__conflict_solve=None,**kw): |
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246 | 247 | """S.merge(data,conflict,k=v1,k=v2,...) -> merge data and k=v into S. |
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247 | 248 | |
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248 | 249 | This is similar to update(), but much more flexible. First, a dict is |
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249 | 250 | made from data+key=value pairs. When merging this dict with the Struct |
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250 | 251 | S, the optional dictionary 'conflict' is used to decide what to do. |
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251 | 252 | |
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252 | 253 | If conflict is not given, the default behavior is to preserve any keys |
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253 | 254 | with their current value (the opposite of the update method's |
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254 | 255 | behavior). |
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255 | 256 | |
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256 | 257 | conflict is a dictionary of binary functions which will be used to |
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257 | 258 | solve key conflicts. It must have the following structure: |
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258 | 259 | |
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259 | 260 | conflict == { fn1 : [Skey1,Skey2,...], fn2 : [Skey3], etc } |
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260 | 261 | |
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261 | 262 | Values must be lists or whitespace separated strings which are |
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262 | 263 | automatically converted to lists of strings by calling string.split(). |
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263 | 264 | |
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264 | 265 | Each key of conflict is a function which defines a policy for |
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265 | 266 | resolving conflicts when merging with the input data. Each fn must be |
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266 | 267 | a binary function which returns the desired outcome for a key |
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267 | 268 | conflict. These functions will be called as fn(old,new). |
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268 | 269 | |
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269 | 270 | An example is probably in order. Suppose you are merging the struct S |
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270 | 271 | with a dict D and the following conflict policy dict: |
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271 | 272 | |
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272 | 273 | S.merge(D,{fn1:['a','b',4], fn2:'key_c key_d'}) |
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273 | 274 | |
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274 | 275 | If the key 'a' is found in both S and D, the merge method will call: |
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275 | 276 | |
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276 | 277 | S['a'] = fn1(S['a'],D['a']) |
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277 | 278 | |
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278 | 279 | As a convenience, merge() provides five (the most commonly needed) |
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279 | 280 | pre-defined policies: preserve, update, add, add_flip and add_s. The |
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280 | 281 | easiest explanation is their implementation: |
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281 | 282 | |
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282 | 283 | preserve = lambda old,new: old |
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283 | 284 | update = lambda old,new: new |
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284 | 285 | add = lambda old,new: old + new |
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285 | 286 | add_flip = lambda old,new: new + old # note change of order! |
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286 | 287 | add_s = lambda old,new: old + ' ' + new # only works for strings! |
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287 | 288 | |
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288 | 289 | You can use those four words (as strings) as keys in conflict instead |
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289 | 290 | of defining them as functions, and the merge method will substitute |
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290 | 291 | the appropriate functions for you. That is, the call |
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291 | 292 | |
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292 | 293 | S.merge(D,{'preserve':'a b c','add':[4,5,'d'],my_function:[6]}) |
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293 | 294 | |
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294 | 295 | will automatically substitute the functions preserve and add for the |
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295 | 296 | names 'preserve' and 'add' before making any function calls. |
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296 | 297 | |
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297 | 298 | For more complicated conflict resolution policies, you still need to |
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298 | 299 | construct your own functions. """ |
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299 | 300 | |
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300 | 301 | data_dict = Struct.__make_dict(self,__loc_data__,**kw) |
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301 | 302 | |
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302 | 303 | # policies for conflict resolution: two argument functions which return |
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303 | 304 | # the value that will go in the new struct |
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304 | 305 | preserve = lambda old,new: old |
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305 | 306 | update = lambda old,new: new |
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306 | 307 | add = lambda old,new: old + new |
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307 | 308 | add_flip = lambda old,new: new + old # note change of order! |
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308 | 309 | add_s = lambda old,new: old + ' ' + new |
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309 | 310 | |
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310 | 311 | # default policy is to keep current keys when there's a conflict |
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311 | 312 | conflict_solve = list2dict2(self.keys(),default = preserve) |
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312 | 313 | |
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313 | 314 | # the conflict_solve dictionary is given by the user 'inverted': we |
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314 | 315 | # need a name-function mapping, it comes as a function -> names |
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315 | 316 | # dict. Make a local copy (b/c we'll make changes), replace user |
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316 | 317 | # strings for the three builtin policies and invert it. |
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317 | 318 | if __conflict_solve: |
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318 | 319 | inv_conflict_solve_user = __conflict_solve.copy() |
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319 | 320 | for name, func in [('preserve',preserve), ('update',update), |
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320 | 321 | ('add',add), ('add_flip',add_flip), ('add_s',add_s)]: |
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321 | 322 | if name in inv_conflict_solve_user.keys(): |
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322 | 323 | inv_conflict_solve_user[func] = inv_conflict_solve_user[name] |
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323 | 324 | del inv_conflict_solve_user[name] |
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324 | 325 | conflict_solve.update(Struct.__dict_invert(self,inv_conflict_solve_user)) |
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325 | 326 | #print 'merge. conflict_solve: '; pprint(conflict_solve) # dbg |
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326 | 327 | #print '*'*50,'in merger. conflict_solver:'; pprint(conflict_solve) |
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327 | 328 | for key in data_dict: |
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328 | 329 | if key not in self: |
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329 | 330 | self[key] = data_dict[key] |
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330 | 331 | else: |
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331 | 332 | self[key] = conflict_solve[key](self[key],data_dict[key]) |
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332 | 333 | |
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333 | 334 | def has_key(self,key): |
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334 | 335 | """Like has_key() dictionary method.""" |
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335 | 336 | return self.__dict__.has_key(key) |
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336 | 337 | |
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337 | 338 | def hasattr(self,key): |
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338 | 339 | """hasattr function available as a method. |
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339 | 340 | |
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340 | 341 | Implemented like has_key, to make sure that all available keys in the |
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341 | 342 | internal dictionary of the Struct appear also as attributes (even |
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342 | 343 | numeric keys).""" |
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343 | 344 | return self.__dict__.has_key(key) |
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344 | 345 | |
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345 | 346 | def items(self): |
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346 | 347 | """Return the items in the Struct's dictionary, in the same format |
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347 | 348 | as a call to {}.items().""" |
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348 | 349 | return self.__dict__.items() |
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349 | 350 | |
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350 | 351 | def keys(self): |
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351 | 352 | """Return the keys in the Struct's dictionary, in the same format |
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352 | 353 | as a call to {}.keys().""" |
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353 | 354 | return self.__dict__.keys() |
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354 | 355 | |
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355 | 356 | def values(self,keys=None): |
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356 | 357 | """Return the values in the Struct's dictionary, in the same format |
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357 | 358 | as a call to {}.values(). |
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358 | 359 | |
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359 | 360 | Can be called with an optional argument keys, which must be a list or |
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360 | 361 | tuple of keys. In this case it returns only the values corresponding |
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361 | 362 | to those keys (allowing a form of 'slicing' for Structs).""" |
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362 | 363 | if not keys: |
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363 | 364 | return self.__dict__.values() |
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364 | 365 | else: |
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365 | 366 | ret=[] |
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366 | 367 | for k in keys: |
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367 | 368 | ret.append(self[k]) |
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368 | 369 | return ret |
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369 | 370 | |
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370 | 371 | def get(self,attr,val=None): |
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371 | 372 | """S.get(k[,d]) -> S[k] if S.has_key(k), else d. d defaults to None.""" |
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372 | 373 | try: |
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373 | 374 | return self[attr] |
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374 | 375 | except KeyError: |
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375 | 376 | return val |
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376 | 377 | |
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377 | 378 | def setdefault(self,attr,val=None): |
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378 | 379 | """S.setdefault(k[,d]) -> S.get(k,d), also set S[k]=d if not S.has_key(k)""" |
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379 | 380 | if not self.has_key(attr): |
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380 | 381 | self[attr] = val |
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381 | 382 | return self.get(attr,val) |
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382 | 383 | |
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383 | 384 | def allow_new_attr(self, allow = True): |
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384 | 385 | """ Set whether new attributes can be created inside struct |
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385 | 386 | |
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386 | 387 | This can be used to catch typos by verifying that the attribute user tries to |
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387 | 388 | change already exists in this Struct. |
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388 | 389 | """ |
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389 | 390 | self['__allownew'] = allow |
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390 | 391 | |
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391 | 392 | |
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392 | 393 | # end class Struct |
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393 | 394 |
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