Zip function not returning expected result in Python?

Question

I have two lists:

a = ['a', 'b', 'c']
b = [1]

I want my output as:

a, 1
b, 1
c, 1

Tried doing this:

for i, j in zip(a, b):
    print i, j

I get only a, 1. How can I make it right?

This is my actual scenario:

 if request.POST.get('share'):
            choices = request.POST.getlist('choice')
            person = request.POST.getlist('select')
            person = ''.join(person)
            person1 = User.objects.filter(username=person)
            for i, j in izip_longest(choices, person1, fillvalue=person1[-1]):
                start_date = datetime.datetime.utcnow().replace(tzinfo=utc)
                a = Share(users_id=log_id, files_id=i, shared_user_id=j.id, shared_date=start_date)
                a.save()
            return HttpResponseRedirect('/uploaded_files/')

I am not sure what type of object does User.objects.filter(username=person) returns, may be it returns an iterator? — Ashwini Chaudhary
– Ashwini Chaudhary, Commented Jan 23, 2013 at 6:35

Ashwini Chaudhary · Accepted Answer · 2013-01-23 06:56:19Z

5

You should probably use itertools.izip_longest() here:

In [155]: a = ['a', 'b', 'c']

In [156]: b = [1]

In [158]: for x,y in izip_longest(a,b,fillvalue=b[-1]):
   .....:     print x,y
   .....:     
a 1
b 1
c 1

In case of zip() as the length of b is just one, so it is going to return only one result. i.e it's result length equals min(len(a),len(b))

But in case of izip_longest the result length is max(len(a),len(b)), if fillvalue is not provided then it returns None.

edited Jan 23, 2013 at 6:56

answered Jan 23, 2013 at 6:25

Ashwini Chaudhary

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1 Comment

Ashwini Chaudhary Over a year ago

@user1881957 eh! never heard of that error before, you can use b[0].

Klaus-Dieter Warzecha · Accepted Answer · 2013-01-23 08:24:58Z

1

OK, i'm late by at least one hour, but what about this idea:

a = ['a', 'b', 'c']
b = [1]

Since the docs on zip state

The returned list is truncated in length to the length of the shortest argument sequence.

what about turning the list a to the shorter argument? And since everything is shorter than a cycle that runs forever, let's try

import itertools

d = zip(a, itertools.cycle(b))

Thanks to Ashwini Chaudhary for bringing the itertools to my attention ;)

answered Jan 23, 2013 at 8:24

Klaus-Dieter Warzecha

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