Question

I have two lists that are already sorted how they need to be, and i need them put into one file, like this example:

list1 = [a, b, c, d, e]
list2 = [1, 2, 3, 4, 5]

output file should look like:

a1
b2
c3
d4
e5

im fairly new to python, so im not really all that sure how to do file writing. I read using with open(file, 'w') as f: is a better/easier way to start the writing block, but i am unsure how to merge the lists and print them as such. I could probably merge them into a third list and print that one to the file using print>>f, item but i wanted to see if there was as simpler way.

Thank you!

Late edit: looking at my lists, they wont always be the same length, but all the data needs printed regardless. So if list2 went to 7 then then the output would need to be:

a1
b2
c3
d4
e5
6
7

or vice versa, where list1 may be longer then list2.

Answer 1

Use the zip() function to combine (ie zip) your two lists. E.g.,

list1 = ['a', 'b', 'c', 'd', 'e']
list2 = [1, 2, 3, 4, 5]

zip(list1, list2)

gives:

[('a', 1), ('b', 2), ('c', 3), ('d', 4), ('e', 5)]

you can then format the output to suit your needs.

for i,j in zip(list1, list2):
    print '%s%d' %(i,j)

yielding:

a1
b2
c3
d4
e5

Update:

If your lists are unequal length, this approach using
itertools.izip_longest() might work for you:

import itertools
list1 = ['a', 'b', 'c', 'd', 'e']
list2 = [1, 2, 3]

for i,j in itertools.izip_longest(list1, list2): 
    if i: sys.stdout.write('%s' %i)
    if j: sys.stdout.write('%d' %j)
    sys.stdout.write('\n')

gives:

a1
b2
c3
d
e 

Note, if you were using Python 3, there is a nice way to use the print() function. I am using write() here to avoid extra blank spaces between items.