Is this the equivalent of a copy constructor in Python?

Question

I'm reviewing some old python code and came accross this 'pattern' frequently:

class Foo(object):
    def __init__(self, other = None):
        if other:
            self.__dict__ = dict(other.__dict__)

Is this how a copy constructor is typically implemented in Python?

Relevant: http://stackoverflow.com/questions/1241148/copy-constructor-in-python — Abhijeet Rastogi, Feb 03 '12 at 16:48

score 5 · Answer 1 · answered Feb 03 '12 at 20:25

5

Note that the attributes aren't copied, they are shared.

>>> a = Foo()
>>> a.x=[1,2,3]
>>> b = Foo(a)
>>> b.x[2] = 4
>>> a.x
[1, 2, 4]

answered Feb 03 '12 at 20:25

Reinstate Monica

score 4 · Accepted Answer · answered Feb 03 '12 at 16:53

This is a way to copy all attributes from one object to another one. However note that:

The object passed to the __init__ method may have any type (not the same type as the object being created).
Only object attributes are copied (class attributes and methods are not).

2 Answers2