How to apply function to elements of a list?

Question

I want to apply a function to all elements in the list, but I want to actually change the elements (which are objects), not view results. I think this is the problem with using map() or list comprehensions.

class Thing(object):
    pass

# some collection of things
my_things

# they are all big...

# produces SyntaxError: invalid syntax
[i.size = "big" for i in my_things]

# produces SyntaxError: lambda cannot contain assignment
map(lambda i: i.size="big", [i for i in my_things]) 

# no error, but is it the preferred way?
for i in my_things:
    i.size="big"

What is the way to do this?

Answer 1

And what's wrong with

for i in my_things:
    i.size = "big"

You don't want to use neither map nor list comprehansion because they actually create new lists. And you don't need that overhead, do you?

Answer 2

You could use the __setattr__ method to assign the attribute in a list comprehension. Although, according to some SO threads, using list comprehensions without using the output is not pythonic.

[i.__setattr__('size', 'big') for i in my_things]