Cleanest way to return a tuple containing a particular element?

Question

In python, if I have a tuple of tuples, like so:

((1, 'foo'), (2, 'bar'), (3, 'baz'))

what is the most efficient/clean/pythonic way to return the 0th element of a tuple containing a particular 1st element. I'm assuming it can be done as a simple one-liner.

In other words, how do I return 2 using 'bar'?

---

This is the clunky equivalent of what I'm looking for, in case it wasn't clear:

for tup in ((1, 'foo'), (2, 'bar'), (3, 'baz')):
    if tup[1] == 'bar':
        tup[0]

Answer 1

Use a list comprehension if you want all such values:

>>> lis = ((1, 'foo'), (2, 'bar'), (3, 'baz'))
>>> [x[0] for x in lis if x[1]=='bar' ]
[2]

If you want only one value:

>>> next((x[0] for x in lis if x[1]=='bar'), None)
2

If you're doing this multiple times then convert that list of tuples into a dict:

>>> d = {v:k for k,v in ((1, 'foo'), (2, 'bar'), (3, 'baz'))}
>>> d['bar']
2
>>> d['foo']
1

Answer 2

>>> lis = ((1, 'foo'), (2, 'bar'), (3, 'baz'))
>>> dict(map(reversed, lis))['bar']
2