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I have a list L = [a, b, c] and I want to generate a list of tuples :
[(a,a), (a,b), (a,c), (b,a), (b,b), (b,c)...]
I tried doing L * L but it didn't work. Can someone tell me how to get this in python.
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We can simply get the product of two lists using for loop. Through for loop, we can iterate through the list. Similarly, with every iteration, we can multiply the elements from both lists. For this purpose, we can use Zip Function.
Lists and strings have a lot in common. They are both sequences and, like pythons, they get longer as you feed them. Like a string, we can concatenate and multiply a Python list.
Method #2 : Using map() + operator.mul This is similar to the above function but uses the operator. mul to multiply each element to other element from the other list of K formed before applying the map function.
You can do it with a list comprehension:
[ (x,y) for x in L for y in L]
edit
You can also use itertools.product as others have suggested, but only if you are using 2.6 onwards. The list comprehension will work will all versions of Python from 2.0. If you do use itertools.product bear in mind that it returns a generator instead of a list, so you may need to convert it (depending on what you want to do with it).
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The itertools module contains a number of helpful functions for this sort of thing. It looks like you may be looking for product:
>>> import itertools
>>> L = [1,2,3]
>>> itertools.product(L,L)
<itertools.product object at 0x83788>
>>> list(_)
[(1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3)]
Take a look at the itertools module, which provides a product member.
L =[1,2,3]
import itertools
res = list(itertools.product(L,L))
print(res)
Gives:
[(1,1),(1,2),(1,3),(2,1), .... and so on]
Two main alternatives:
>>> L = ['a', 'b', 'c']
>>> import itertools
>>> list(itertools.product(L, L))
[('a', 'a'), ('a', 'b'), ('a', 'c'), ('b', 'a'), ('b', 'b'), ('b', 'c'), ('c', 'a'), ('c', 'b'), ('c', 'c')]
>>> [(one, two) for one in L for two in L]
[('a', 'a'), ('a', 'b'), ('a', 'c'), ('b', 'a'), ('b', 'b'), ('b', 'c'), ('c', 'a'), ('c', 'b'), ('c', 'c')]
>>>
the former one needs Python 2.6 or better -- the latter works in just about any Python version you might be tied to.
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