MRAB wrote:
Kottiyath wrote:
Hi,
I have 2 lists
a = [(4, 1), (7, 3), (3, 2), (2, 4)]
b = [2, 4, 1, 3]
Now, I want to order _a_ (a[1]) based on _b_.
i.e. the second element in tuple should be the same as b.
i.e. Output would be [(3, 2), (2, 4), (4, 1), (7, 3)]
I did the same as follows:
l = len(a) * [None]
for (k, v) in a:
... for i, e in enumerate(b):
... if e == v:
... l[i] = (k, v)
This works, but the code -for python- looks very kludgy.
I thought for ~2 hours to see whether I can do it in a line or 2,
but I cannot seem to find a mechanism.
Can someone help me out?
How about:
>>> a = [(4, 1), (7, 3), (3, 2), (2, 4)]
>>> b = [2, 4, 1, 3]
>>> d = dict((v, k) for k, v in a)
>>> c = [(d[s], s) for s in b]
>>> c
[(3, 2), (2, 4), (4, 1), (7, 3)]
Understanding how it works is left as an exercise for the reader. :-)
Actually, a more general solution is:
>>> a = [(4, 1), (7, 3), (3, 2), (2, 4)]
>>> b = [2, 4, 1, 3]
>>> d = dict((t[1], t) for t in a)
>>> c = [d[s] for s in b]
>>> c
[(3, 2), (2, 4), (4, 1), (7, 3)]
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