How do I combine two lists into a dictionary in Python

Question

I have two lists of the same length    1 2 3 4  and  a b c d   I want to create a dictionary where I have  1 a  2 b  3 c  4 d   What s the best way to do this

User · Answer

If there are duplicate keys in the first list that map to different values in the second list, like a 1-to-many relationship, but you need the values to be combined or added or something instead of updating, you can do this:

i = iter(["a", "a", "b", "c", "b"])
j = iter([1,2,3,4,5])
k = list(zip(i, j))
for (x,y) in k:
    if x in d:
        d[x] = d[x] + y #or whatever your function needs to be to combine them
    else:
        d[x] = y

In that example, d == {'a': 3, 'c': 4, 'b': 8}

User · Answer

dict zip  1 2 3 4     a    b    c    d       http   docs python org library functions html

User · Answer

gt  gt  gt  dict zip  1  2  3  4     a    b    c    d      1   a   2   b   3   c   4   d     If they are not the same size  zip will truncate the longer one

User · Answer

dict zip  1 2 3 4    a b c d      If the lists are big you should use itertools izip   If you have more keys than values  and you want to fill in values for the extra keys  you can use itertools izip longest   Here  a  b  c  and d are variables -- it will work fine  so long as they are defined   but you probably meant   a   b   c   d   if you want them as strings   zip takes the first item from each iterable and makes a tuple  then the second item from each  etc  etc   dict can take an iterable of iterables  where each inner iterable has two items -- it then uses the first as the key and the second as the value for each item

User · Answer

I found myself needing to create a dictionary of three lists  latitude  longitude  and a value   with the following doing the trick    gt  lat    45 3 56 2 23 4 60 4   gt  lon    134 6 128 7 111 9 75 8   gt  val    3 6 2 5   gt  dict zip zip lat lon  val     56 2  128 7   6   60 4  75 8   5   23 4  111 9   2   45 3  134 6   3    or similar to the above examples    gt  list1    1 2 3 4   gt  list2    1 2 3 4   gt  list3     a   b   c   d    gt  dict zip zip list1 list2  list3     3  3    c    4  4    d    1  1    a    2  2    b     Note  Dictionaries are  orderless   but if you would like to view it as  sorted   refer to THIS question if you d like to sort by key  or THIS question if you d like to sort by value

User · Answer

I don t know about best  simplest  fastest  most readable    but one way would be   dict zip  1  2  3  4    a  b  c  d

[python] How do I combine two lists into a dictionary in Python?

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