views:

126

answers:

5

trying to make dictionary with 2 list one being the key and one being the value but I'm having a problem. This is what I have so far:

d={}
for num in range(10):
    for nbr in range(len(key)):
     d[num]=key[nbr]

say my key is a list from 1 to 9 and value list is [2,4,0,9,6,6,8,6,4,5] how do i assign so it that its like {0:2, 1:4, etc...}

A: 

should be something like

dict(zip(a,b))
Jimmy
+10  A: 

zip() to the rescue!

>>> k = range(1,10)   # or some list or iterable of sorts
>>> v = [2,4,0,9,6,6,8,6,4,5]
>>> d = dict(zip(k,v))
>>> d
{1: 2, 2: 4, 3: 0, 4: 9, 5: 6, 6: 6, 7: 8, 8: 6, 9: 4}
>>>

For more details, see zip() built-in function, in Python documentation.

Note, regarding range() and the list of "keys".
The question reads "key is a list from 1 to 9" (i.e. 9 distinct keys) but the value list shows 10 distinct values. This provides the opportunity to discuss two points of "detail":

  • the range() function in the snippet above will produce the 1 through 9 range, that is because the starting value (1, here), if provided, is always included, whereas the ending value (10, here) is never included.
  • the zip() function stops after the iteration which includes the last item of the shortest iterable (in our case, omitting '5', the last value of the list)
mjv
+2  A: 
values = [2,4,0,9,6,6,8,6,4,5]
d = dict(zip(range(10), values))
int3
A: 
mydict = dict(zip(range(10), [2,4,0,9,6,6,8,6,4,5]))
Tim Pietzcker
+6  A: 

If you are mapping indexes specifically, use the enumerate builtin function instead of zip/range.

dict(enumerate([2,4,0,9,6,6,8,6,4,5]))
fengb
Hard to see why you'd need to create a dict that uses a range for a key, unless you're passing it to something that can't use a list.
Mark Ransom