pickling class method

Question

I have a class whose instances need to format output as instructed by the user. There\'s a default format, which can be overridden. I implemented it like this:

Answer 1

For pickling of class instances or functions (and therefore methods), Python's pickle depend that their name is available as global variables - the reference to the method in the dictionary points to a name that is not available in the global name space - which iis better said "module namespace" -

You could circunvent that by customizing the pickling of your class, by creating teh "__setstate__" and "__getstate__" methods - but I think you be better, since the formatting function does not depend on any information of the object or of the class itself (and even if some formatting function does, you could pass that as parameters), and define a function outside of the class scope.

This does work (Python 3.2):

def default_float_format( x):
    return '{:.2%}'.format(x)

class A:

  def __init__(self, params):
    # ...
    # by default printing all float values as percentages with 2 decimals
    self.format_functions = {float: default_float_format}
  def __str__(self):
    # uses self.format_functions to format output
    pass

a = A(1)
pickle.dumps(a)