How to use pythons map with a non-iterable and iterable set of parameters?

Question

To make a simple example, I don't care about the practicality, just the implemenation. Say I create some class with a few methods. I want to create a list containing whether or not they're callable. So I can take this example from: Finding what methods an object has

[method for method in dir(object) if callable(getattr(object, method))]

It's great for what it does, but if for the heck of it, I want to use map and I have object, which is a non-iterable item...

map(callable,map(getattr,object,dir(object)))

To focus on the real problem:

I have an iterable list, and a non iterable item. What is the best solution that lets me use some non-iterable item and an iterable item, so that I can utilize map?

I have no idea what you're asking or what you're trying to do. — Falmarri, Nov 10 '10 at 22:38
@Falmarri: You're not alone. This seems more a riddle than a question. — Glenn Maynard, Nov 10 '10 at 22:49

score 4 · Accepted Answer · answered Nov 10 '10 at 22:37

4

I will admit to not understanding why, since the LC works, but:

map(lambda x: callable(getattr(object, x)), dir(object))

answered Nov 10 '10 at 22:37

Ignacio Vazquez-Abrams

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Awesome. Just what I wanted. Thanks : ) – pyInTheSky Nov 10 '10 at 22:42
Different application, I just pulled that as an example. I wanted to use map w/ a few non-iterable items. – pyInTheSky Nov 10 '10 at 22:48
The main reason for the question was to try some optimizations. Interestingly enough, the LC was actually faster when running through a longer sequence. – pyInTheSky Nov 11 '10 at 16:54

score 0 · Answer 2 · answered Nov 10 '10 at 22:48

0

If you're not clear on what the lambda above does, equivalently you could define:

def myMap(fun1,obj,iterlist):
        def fun2(x):
            return fun1(obj,x)
        return map(fun2,iterlist)

And then, call

map(callable,myMap(getattr,object,dir(object)))

for example:

map(callable,myMap(getattr,myMap,dir(myMap)))

Though using lambda is more pythonic.

answered Nov 10 '10 at 22:48

highBandWidth

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"Though using lambda is more pythonic." ... according to who? – detly Nov 10 '10 at 23:39

score 0 · Answer 3 · answered Nov 10 '10 at 23:52

Sometime LC is just the right way to do it

>>> from itertools import izip, repeat, starmap
>>> map(callable, starmap(getattr, zip(repeat(object), dir(object))))

This also works, but requires dir(object) twice

>>> map(callable, map(getattr, repeat(object, len(dir(object))), dir(object)))

and finally

>>> from itertools import izip_longest
>>> map(callable, starmap(getattr, izip_longest([], dir(object), fillvalue=object)))

How to use pythons map with a non-iterable and iterable set of parameters?

3 Answers3