Python: merge nested lists

5
votes

beginner to python here.

I have 2 nested lists that I want to merge:

list1 = ['a',
         (b, c),
         (d, e),
         (f, g, h) ]

list2 = [(p,q),
         (r, s),
         (t),
         (u, v, w) ]

the output I am looking for is:

list3 = [(a, p, q),
         (b, c, r, s),
         (d, e, t),
         (f, g, h, u, v, w) ]

Can this be done without any external libraries? note: len(list1) = len(list2)

4
pythonmergenested-lists
beginner to python here. - This means you should read the tutorial. - Björn Pollex
Hi. I have read the tuts. I know how to merge simple lists. But don't know how to go about with nested lists. - Rishav Sharan
Also, the first element of list1 is a string in your example, but after the merge it seems to be an object. - Björn Pollex
... which is valid if a == 'a', but then the rest doesn't make any sense. (t) is not a tuple, btw. -1. - Fred Foo

4 Answers

17
votes

Use the power of the zip function and list comprehensions:

list1 = [('a', ),
        ('b', 'c'),
        ('d', 'e'),
        ('f', 'g', 'h') ]

list2 = [('p', 'q'),
        ('r', 's'),
        ('t', ),
        ('u', 'v', 'w') ]

print [a + b for a, b in zip(list1, list2)]
4
votes
from operator import add
list3 = map(add, list1, list2)
0
votes

If the order within an inner list/tuple is not important, you can use the mathematical set operations.

print [tuple(set(a)|set(b)) for a,b in zip(x,y)]

The set(a)|set(b) converts the iterables a and b to sets and takes the union of the two sets. They are then converted back to tuple as desired in the output format.

As you are a beginner to python, it is strongly recommended to master list comprehensions. It is way too powerful and concise. In addition to making your code more 'pythonic', list comprehensions can act as a friendlier replacement to 'map' and 'filter' functions.

0
votes

Easy One

list_3 = []
list_3.extend(list_1 + list_2)