Iteration over list of strings in Python

Question

Let us have a list of strings: fruit = ["apple", "orange", "banana"]. I would like to have an output that prints out all the possible pairs, i.e.

apple - apple, apple - orange, apple - banana, 
orange - orange, orange - banana, 
banana - banana

My idea was to enumerate fruit and do the following:

for icnt, i in fruit:
    jcnt = icnt
    j = i
    print ("icnt: %d, i: %s", icnt, i)
    for jcnt, j in fruit:
        print ("i: %s, j: %s", i, j)

Expectantly the string does not start from the icnt-th position but from the start. How to make the second loop to start from the i-th string?

As @Jean-FrançoisFabre says, you should use itertools.combinations but to answer your question, you have to slice the fruit list in the second loop like so: for jcnt, j in enumerate(fruit[icnt:]): Also if you are going to use enumerate, do so. — Ma0
– Ma0, Commented Jan 11, 2017 at 15:11

Jean-François Fabre · Accepted Answer · 2017-01-11 15:10:23Z

3

use itertools.combinations_with_replacement to do this:

import itertools

for a,b in itertools.combinations_with_replacement(["apple", "orange", "banana"],2):
    print("{} - {}".format(a,b))

output:

apple - apple
apple - orange
apple - banana
orange - orange
orange - banana
banana - banana

or itertools.combinations if you don't want any repeats:

apple - orange
apple - banana
orange - banana

BTW your fixed code would look like this with enumerate:

fruit = ["apple", "orange", "banana"]

for icnt, i in enumerate(fruit):
     for jcnt in range(icnt,len(fruit)):
        print ("{} - {}".format(i, fruit[jcnt]))

answered Jan 11, 2017 at 15:10

Jean-François Fabre♦

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Comments

DeepSpace · Accepted Answer · 2017-01-11 15:14:15Z

2

Don't reinvent the wheel. Use itertools:

from itertools import combinations_with_replacement

fruit = ["apple", "orange", "banana"]

print('\n'.join((' - '.join(perm) for perm in combinations_with_replacement(fruit, 2))))
# apple - apple
# apple - orange
# apple - banana
# orange - orange
# orange - banana
# banana - banana

edited Jan 11, 2017 at 15:14

answered Jan 11, 2017 at 15:10

DeepSpace

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2 Comments

Moses Koledoye Over a year ago

This isn't exactly what is shown in the OP e.g you don't have apple-apple

DeepSpace Over a year ago

@MosesKoledoye Thanks. got that fixed

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