python one line function definition

Question

This must be simple, but as an only occasional python user, fighting some syntax. This works:

def perms (xs):     for x in itertools.permutations(xs): yield list(x)  

But this won't parse:

def perms (xs): for x in itertools.permutations(xs): yield list(x)  

Is there some restriction on the one-line function syntax? The body definition (for...) can be either two or one line by itself, and the def: can be one or two lines with a simple body, but combining the two fails. Is there a syntax rule that excludes this?

Answer 1

If you must have one line just make it a lambda:

perms = lambda xs: (list(x) for x in itertools.permutations(xs)) 

Quite often, when you have a short for loop for generating data you can replace it with either list comprehension or a generator expression for approximately the same legibility in slightly less space.

Answer 2

Yes, there are restrictions. No, you can't do that. Simply put, you can skip one line feed but not two.

See here.

The reason for this is that it would allow you to do

if test1: if test2: print x else:     print y 

Which is ambiguous.