CODEWITHSUNDEEP
python
kc64
kc64

Reputation: 33

using python2.7 zip on list returns different results

I'm puzzled. I've executed zip on two sets of lists and get different results. I'm hoping a seasoned expert can help me understand where my thinking has gone wrong.

s1 and s2 represent two phrases which will always be one to three words long. I need to stack the words of the phrases into columns (with the stack bottom-justified). I don't understand why the two calls to zip return different results. I've used repr and both function parameters appear identical.

>>> s1 = 'a b'
>>> s2 = 'c d'
>>> s1.split(' '),s2.split(' ')
(['a', 'b'], ['c', 'd'])

>>> tokens = s1.split(' '),s2.split(' ')
>>> tokens
(['a', 'b'], ['c', 'd'])

>>> zip(s1.split(' '),s2.split(' '))
[('a', 'c'), ('b', 'd')]

>>> zip(tokens)
[(['a', 'b'],), (['c', 'd'],)]

Upvotes: 0

Views: 63

Answers (2)

g.d.d.c
g.d.d.c

Reputation: 47988

The way returns are displaying in your interactive console is throwing you off a bit.

# This calls zip with 2 arguments.
>>> zip(s1.split(' '),s2.split(' '))
[('a', 'c'), ('b', 'd')]

# This calls zip with 1 argument.
>>> zip(tokens)
[(['a', 'b'],), (['c', 'd'],)]

# This unpacks the tuple and calls zip with 2 arguments again,
>>> zip(*tokens)
[('a', 'c'), ('b', 'd')]

Upvotes: 1

Pavel
Pavel

Reputation: 7552

you've got to read the parenthesis very carefully:

>>> tokens = s1.split(' '),s2.split(' ')
>>> tokens
(['a', 'b'], ['c', 'd'])

the return value was a single tuple consisting of two lists

so, you're passing a single element to zip. if you address the elements separately, you get

>>> zip(tokens[0], tokens[1])
[('a', 'c'), ('b', 'd')]

>>> zip(*tokens)
[('a', 'c'), ('b', 'd')]

Upvotes: 0

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