Allowing the repr() of my class's instances to be parsed by eval()

Question

Say I have defined a class myself and I defined a __repr__ method for it. I want to about convert it back to my object. I know that object serialization may be a good way of doing so (using the json module) but is there anyway I can use the built-in eval function to achieve this?

I am sorry for ambiguity here, What I mean is I want to make my object eval-able here. — Bob Fang, Feb 01 '13 at 23:27

kindall · Accepted Answer · 2013-02-02T17:23:31.383

4

Write your __repr__() so it creates a valid Python expression for instantiating your object.

class MyClass(object):
    def __init__(self, a, b):
        self.a = a
        self.b = b
    def __repr__(self):
        return "%s(%r, %r)" % (type(self).__name__, self.a, self.b)

Obviously this relies on the values you're using having their own reasonable repr().

You don't have to define any special eval()—just pass in whatever you get from repr().

edited Feb 02 '13 at 17:23

answered Feb 01 '13 at 23:13

kindall

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if you try this, you will get an error saying NameError: name 'instance' is not defined – Bob Fang Feb 01 '13 at 23:26
There is not anything called `instance` in that code, so that's not where that error is coming from. – kindall Feb 02 '13 at 01:07
1

@kindall: he's probably using an old-style class. – DSM Feb 02 '13 at 01:39

Allowing the repr() of my class's instances to be parsed by eval()

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