You could use map
instead of the for
loop you've shown, but since you do not appear to use the result of item.my_func()
, this is not recommended. map
should be used if you want to apply a function without side-effects to all elements of a list. In all other situations, use an explicit for-loop.
Also, as of Python 3.0 map
returns a generator, so in that case map
will not behave the same (unless you explicitly evaluate all elements returned by the generator, e.g. by calling list
on it).
Edit: kibibu asks in the comments for a clarification on why map
's first argument should not be a function with side effects. I'll give answering that question a shot:
map
is meant to be passed a function f
in the mathematical sense. Under such circumstances it does not matter in which order f
is applied to the elements of the second argument (as long as they are returned in their original order, of course). More importantly, under those circumstances map(g, map(f, l))
is semantically equivalent to map(lambda x: g(f(x)), l)
, regardless of the order in which f
and g
are applied to their respective inputs.
E.g., it doesn't matter whether map
returns and iterator or a full list at once. However, if f
and/or g
cause side effects, then this equivalence is only guaranteed if the semantics of map(g, map(f, l))
are such that at any stage g
is applied to the first n elements returned by map(f, l)
before map(f, l)
applies f
to the (n + 1)st element of l
. (Meaning that map
must perform the laziest possible iteration---which it does in Python 3, but not in Python 2!)
Going one step further: even if we assume the Python 3 implementation of map
, the semantic equivalence may easily break down if the output of map(f, l)
is e.g. passed through itertools.tee
before being supplied to the outer map
call.
The above discussion may seem of a theoretic nature, but as programs become more complex, they become more difficult to reason about and therefore harder to debug. Ensuring that some things are invariant alleviates that problem somewhat, and may in fact prevent a whole class of bugs.
Lastly, map
reminds many people of its truly functional counterpart in various (purely) functional languages. Passing it a "function" with side effects will confuse those people. Therefore, seeing as the alternative (i.e., using an explicit loop) is not harder to implement than a call to map
, it is highly recommended that one restricts use of map
to those cases in which the function to be applied does not cause side effects.