Q:

Swap values in a tuple/list inside a list in python?

I have a tuple/list inside a list like this:
[('foo','bar'),('foo1','bar1'),('foofoo','barbar')]

What is the fastest way in python (running on a very low cpu/ram machine) to swap values like this...
[('bar','foo'),('bar1','foo1'),('barbar','foofoo')]

curently using:
for x in mylist:
    self.maynewlist.append((_(x[1]),(x[0])))

Is there a better or faster way??? 

A:

You could use map:
map (lambda t: (t[1], t[0]), mylist)

Or list comprehension:
[(t[1], t[0]) for t in mylist]

List comprehensions are preferred and supposedly much faster than map when lambda is needed, however note that list comprehension has a strict evaluation, that is it will be evaluated as soon as it gets bound to variable, if you're worried about memory consumption use a generator instead:
g = ((t[1], t[0]) for t in mylist)
#call when you need a value
g.next()

There are some more details here: Python List Comprehension Vs. Map

A:

You can use reversed like this:
tuple(reversed((1, 2)) == (2, 1)

To apply it to a list, you can use map or a list comprehension:
map(tuple, map(reversed, tuples))     # map
[tuple(reversed(x)) for x in tuples]  # list comprehension

If you're interested primarily in runtime speed, I can only recommend that you profile the various approaches and pick the fastest.

