How can I take two tuples to produce a dictionary? [duplicate]

Question

My first thought is to write an interator, or maybe do some list comprehension. But, like every 5-10 line method I write in python, someone can usually point me to a call in the standard library to accomplish the same.

How can I go from two tuples, x and y to a dictionary z?

x = ( 1, 2, 3 )
y = ( 'a', 'b', 'c')

z = { }
for index, value in enumerate(y):
    z[value] = x[index]

print z

# { 'a':1, 'b':2, 'c':3 }

Answer 1

Tuples are iterables. You can use zip to merge two or more iterables into tuples of two or more elements.

A dictionary can be constructed out of an iterable of 2-tuples, so:

#          v values
dict(zip(y,x))
#        ^ keys

This generates:

>>> dict(zip(y,x))
{'c': 3, 'a': 1, 'b': 2}

Note that if the two iterables have a different length, then zip will stop from the moment one of the tuples is exhausted.

You can - as @Wondercricket says - use izip_longest (or zip_longest in python-3.x) with a fillvalue: a value that is used when one of the iterables is exhausted:

from itertools import izip_longest

dict(izip_longest(y,x,fillvalue=''))

So if the key iterable gets exhausted first, all the remaining values will be mapped on the empty string here (so only the last one will be stored). If the value iterable is exhausted first, all remaining keys will here be mapped on the empty string.

Answer 2

You can use a dictionary comprehension:

>>> {y[i]:x[i] for i,_ in enumerate(x)}
{'a': 1, 'b': 2, 'c': 3}