Dynamic assignment of methods in python class

Question

I want to create a bunch of methods in class __init__ method dynamically. Havent had luck so far.

CODE:

class Clas(object):
    def __init__(self):
        for i in ['hello', 'world', 'app']:
            def method():
                print i
            setattr(self, i, method)

Than I crate method and call method that is fitst in list.

>> instance = Clas()

>> instance.hello()

'app'

I expect it to print hello not app. WHat is the problem? In addition, each of these dynamically assigned methods referred to the same function in memory, even if I do copy.copy(method)

Martijn Pieters · Accepted Answer · 2013-03-25 14:47:22Z

6

You need to bind i properly:

for i in ['hello', 'world', 'app']:
    def method(i=i):
        print i
    setattr(self, i, method)

The i variable then is made local to method. Another option is to use a new scope (separate function) generating your method:

def method_factory(i):
    def method():
        print i
    return method 

for i in ['hello', 'world', 'app']:
    setattr(self, i, method_factory(i))

answered Mar 25, 2013 at 14:47

Martijn Pieters

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