How to combine two lists in a single list with different elements in python

Question

I am new to python

I have list_a as ['A','B'] and list_b as ['C','D']

output I have to get is in this format [['AC','BC'],['AD','BD']]

When I tried with this below code:

output = []

for a in ['A','B']:

    for b in ['C','D']:
        if a !=b:
            output.append([a,b])
print output

I Got output as [['A', 'C'], ['A', 'D'], ['B', 'C'], ['B', 'D']]

I am not sure what I am doing wrong.

John1024 · Accepted Answer · 2015-02-06 06:05:44Z

2

Define lists a and b:

>>> a = ['A','B'];  b = ['C','D']

Now, combine them:

>>> [ [x + y for x in a] for y in b ]
[['AC', 'BC'], ['AD', 'BD']]

If you really must do explicit loops:

outer = []
for y in ['C','D']:
    inner = []
    for x in ['A','B']:
        inner.append(x + y)
    outer.append(inner)
print(outer)

This results in:

[['AC', 'BC'], ['AD', 'BD']]

answered Feb 6, 2015 at 6:05

John1024

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1 Comment

Thank you so much for your valuable explanation John

Alex Martelli · Accepted Answer · 2015-02-06 06:08:14Z

0

Mostly, you're looping in the wrong order...

output = []
for b in list_b:
    output.append([a + b for a in list_a])

gives you [['AC', 'BC'], ['AD', 'BD']] as desired.

answered Feb 6, 2015 at 6:08

Alex Martelli

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@Bhanu, great! So please accept either John's sophisticated answer or my simpler one so the question is seen as resolved.