# Ticket #11845: picklefunc.py

File picklefunc.py, 4.5 KB (added by , 9 years ago) |
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1 | r""" |

2 | Pickleable function objects |

3 | |

4 | Provides a pickleable wrapper for function objects. The resulting pickles have |

5 | the same portability restrictions as marshalled code objects (see the marshal |

6 | module in the python standard library) |

7 | |

8 | AUTHORS: |

9 | |

10 | - Nils Bruin (2011-09-24): initial version |

11 | """ |

12 | |

13 | import types |

14 | import marshal |

15 | |

16 | def makecell(value): |

17 | r""" |

18 | return value wrapped in a cell object |

19 | """ |

20 | return (lambda : value).func_closure[0] |

21 | |

22 | class PickleableFunction(object): |

23 | r""" |

24 | Wrapper for functions to make them pickleable |

25 | |

26 | Dynamically defined function objects such as results of lambda expressions |

27 | or from closures, are normally not pickleable. This class provides a |

28 | pickleable wrapper for such function objects. The resulting pickles are only |

29 | portable to the extent that marshalled codeobject are portable (see the |

30 | marshal module in the Python library for a description of the limitations). |

31 | |

32 | INPUT: |

33 | |

34 | - ``f`` - a Python function |

35 | |

36 | OUTPUT: |

37 | |

38 | - A wrapped function that is pickleable |

39 | |

40 | EXAMPLES:: |

41 | |

42 | sage: def f(a,b=0): |

43 | ... "docstring of f" |

44 | ... return a+b |

45 | sage: p=PickleableFunction(f) |

46 | |

47 | The wrapped object is still callable, but less efficient of course:: |

48 | |

49 | sage: p(10,20) |

50 | 30 |

51 | sage: p |

52 | PickleableFunction(<function f at ...>) |

53 | sage: q=loads(dumps(p)) |

54 | |

55 | We cannot expect to hold for reconstructed objects when code is involved: |

56 | |

57 | sage: p == q |

58 | False |

59 | |

60 | But we can throw away the wrapper and call the new object and get the same |

61 | result:: |

62 | |

63 | sage: g=q.function |

64 | sage: g(10,20) |

65 | 30 |

66 | |

67 | Closures of functions are correctly recreated:: |

68 | |

69 | sage: def make_constant(c): |

70 | ....: return lambda inc=0: c+inc |

71 | sage: f=make_constant(5) |

72 | sage: p=PickleableFunction(f) |

73 | sage: q=loads(dumps(p)) |

74 | sage: g=q.function |

75 | sage: g(1) |

76 | 6 |

77 | |

78 | Generators are also pickled correctly:: |

79 | |

80 | sage: def make_counter(c): |

81 | ....: def count(): |

82 | ....: for i in xrange(c): |

83 | ....: yield i |

84 | ....: return count |

85 | sage: f=make_counter(10) |

86 | sage: g=loads(dumps(PickleableFunction(f))).function |

87 | sage: [i for i in g()] |

88 | [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] |

89 | |

90 | """ |

91 | |

92 | def __init__(self,f): |

93 | """ |

94 | """ |

95 | if not(isinstance(f,types.FunctionType)): |

96 | raise ErrorType, "PickleableFunction can only wrap python functions" |

97 | self.function=f |

98 | |

99 | def __call__(self,*args,**kwargs): |

100 | """ |

101 | Calling the wrapper results in calling the wrapped function |

102 | """ |

103 | return self.function(*args,**kwargs) |

104 | |

105 | def __getstate__(self): |

106 | """ |

107 | Implementation of pickle protocol |

108 | """ |

109 | |

110 | #we extract all data from self.function necessary to recreate it. |

111 | f=self.function |

112 | |

113 | code=marshal.dumps(f.func_code) #use marshal to serialize code object |

114 | globs=f.func_globals |

115 | name=f.func_name |

116 | kwargs=f.func_defaults |

117 | if f.func_closure: |

118 | # if there is a closure, unwrap the values from their cells |

119 | closure_tuple=tuple(c.cell_contents for c in f.func_closure) |

120 | else: |

121 | closure_tuple=None |

122 | |

123 | #the produced state is a tuple state such that essentially |

124 | #types.FunctionObject(*state) |

125 | #would recreate the right function object. The "code" and "closure" |

126 | #parameters are recoded in a serializable form. |

127 | #we are ignoring the "globals" of the function object because that |

128 | #is almost certainly not meant to be pickled. |

129 | return (code,None,name,kwargs,closure_tuple) |

130 | |

131 | def __setstate__(self,state): |

132 | """ |

133 | Implementation of pickle protocol |

134 | """ |

135 | |

136 | code,globs,name,kwargs,closure_tuple=state |

137 | code_object=marshal.loads(code) #deserialize code object using marshal |

138 | if globs is None: #no globals means: use present globals |

139 | globs=globals() |

140 | if closure_tuple: |

141 | #closure needs to be a tuple of cell objects |

142 | closure=tuple(makecell(c) for c in closure_tuple) |

143 | else: |

144 | closure=None |

145 | self.function=types.FunctionType(code_object,globs,name,kwargs,closure) |

146 | |

147 | def __repr__(self): |

148 | """ |

149 | return string representation |

150 | """ |

151 | return "PickleableFunction(%s)"%self.function |