CODEWITHSUNDEEP
pythonpython-3.xdictionary
Simple runner
Simple runner

Reputation: 445

Create dictionary from 2 lists

My task: I have 2 lists different size(1,2,3,4 and "qwe","asd","zxc" for example). How I can create dictionary with this lists with next condition: if count of keys more than values- dict[key]=None. If count of values more-just inore it. My code:

list1=[1,2,3,4]
list2=["qwe","asd","zxc"]
dictx={}
for x in range(len(list1)):
if x>len(list2):
    dictx[list1[x]]=None
else:
    dictx[list1[x]]=list2[x]

But I catch error: Traceback (most recent call last): File "", line 5, in dictx[list1[x]]=list2[x] IndexError: list index out of range Where I do mistake?Python 3.4 Upd.It's work, but I try to understand where my mistake in this code. Anybody have thought?

Upvotes: 0

Views: 1609

Answers (2)

venpa
venpa

Reputation: 4318

You can also use itertools.izip_longest as follows:

import itertools
list1=[1,2,3,4]
list2=["qwe","asd","zxc"]
print ({l1:l2 for l1,l2 in itertools.izip_longest(list1,list2,fillvalue=None)})

EDIT: In python 3:

import itertools
list1=[1,2,3,4]
list2=["qwe","asd","zxc"]
print ({l1:l2 for l1,l2 in itertools.zip_longest(list1,list2,fillvalue=None)})

Output:

{1: 'qwe', 2: 'asd', 3: 'zxc', 4: None}

Upvotes: 3

user2357112
user2357112

Reputation: 280837

Pad the value list with Nones using itertools.chain and itertools.repeat, then zip the lists:

from itertools import chain, repeat

d = dict(zip(list1, chain(list2, repeat(None))))

repeat(None) is an infinite iterator that yields None forever.

chain(list2, repeat(None)) is an iterator that yields items from list2, then yields Nones when list2 runs out.

zip(...) returns a list of pairs of corresponding elements from list1 and the padded list2. zip stops when any input runs out, so the input is as long as list1.

Finally, dict(...) takes the list of key-value pairs and makes a dict with those keys corresponding to those values.

Upvotes: 3

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