Python: merge nested lists

Question

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)

*beginner to python here.* - This means you should read the [tutorial](http://docs.python.org/tutorial/). — Björn Pollex, Oct 18 '11 at 11:31
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, Oct 18 '11 at 11:34
Also, the first element of `list1` is a string in your example, but after the merge it seems to be an object. — Björn Pollex, Oct 18 '11 at 11:34
... which is valid if `a == 'a'`, but then the rest doesn't make any sense. `(t)` is not a tuple, btw. -1. — Fred Foo, Oct 18 '11 at 11:35

score 18 · Accepted Answer · answered Oct 18 '11 at 11:34

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)]

score 4 · Answer 2 · answered Oct 18 '11 at 11:37

4

from operator import add
list3 = map(add, list1, list2)

answered Oct 18 '11 at 11:37

John La Rooy

295,403
53
369
502

Or, if you want to avoid the import, `map(tuple.__add__, ...)`. (+1 for not insisting on list comprehensions where `map()` is more readable.) – Sven Marnach Oct 19 '11 at 09:13

score 0 · Answer 3 · answered Feb 22 '21 at 12:21

0

Easy One

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

answered Feb 22 '21 at 12:21

Shah Vipul

625
7
11

score 0 · Answer 4 · answered Oct 18 '11 at 14:22

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.

Python: merge nested lists

4 Answers4

Easy One

Linked

Related