Python: Loop through multiple lists and create a tuple

Question

I have 2 lists of data and I would like to create a tuple for this lists that looks like

ttuple=(1,[4,6,counter])

listA=[1,2,3,4,5,6,7,8,9]
listB=[3,4,5,7,8,9,0,-4,5]
counter=0
for i in range(len(listA)):
     for lista in listA:
         for listb in listB:
              data=(i,[lista,listb,counter])
              myList.append(data)
print(data)

Only the last value is printed. Can someone point to me what I am doing wrong. Its supposed to print tuple list of 9 values like the following. The last number is a counter that increments by 1

(0,[1,3,0),(1,[2,4,0]),(2,[3,5,0])

All i get is the following:

(0,[1,1]),(0,[1,1]),(0,[1,1]), (1,[2,2]),(1,[2,2]),(1,[2,2])

shaktimaan · Accepted Answer · 2014-04-19 03:04:44Z

3

You can use enumerate and zip in conjunction to get what you want:

>>> listA=[1,2,3,4,5,6,7,8,9]
>>> listB=[3,4,5,7,8,9,0,-4,5]
>>> output = []
>>> for i, a in enumerate(zip(listA, listB)):
...     output.append((i, [a[0], a[1], 0]))
...
>>> output
[(0, [1, 3, 0]),
 (1, [2, 4, 0]),
 (2, [3, 5, 0]),
 (3, [4, 7, 0]),
 (4, [5, 8, 0]),
 (5, [6, 9, 0]),
 (6, [7, 0, 0]),
 (7, [8, -4, 0]),
 (8, [9, 5, 0])]

answered Apr 19, 2014 at 3:04

shaktimaan

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1 Comment

don Over a year ago

you really saved the day. Thank you, how can i get in touch so you can help me with another thing I have a problem with

ebarr · Accepted Answer · 2014-04-19 03:08:10Z

1

You can use a list comprehension:

output = [(ii,[b,c,counter]) for ii,(b,c) in enumerate(zip(listA,listB))]

answered Apr 19, 2014 at 3:08

ebarr

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Comments

agrinh · Accepted Answer · 2014-04-19 03:17:56Z

There's two issues with the code you provided (that I can find anyways). Biggest of which is the fact that you produce len(listA) ** 2 * len(listB) elements! You do not have to iterate over listA and listB instead use the index i to access the elements in both lists. Another issue is that myList is not defined (but I assume you just forgot that).

Here's a more fun way of solving this:

from itertools import izip
n = len(min(listA, listB))
result = list(enumerate(izip(listA, listB, xrange(n))))
print(result)

This will however give you tuples everywhere, to match the exact output just do:

from itertools import izip
n = len(min(listA, listB))
result = list(enumerate(list(item) for item in izip(listA, listB, xrange(n))))
print result

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