Question

Edit: I’ve realized my error (if statement, variable x is assigned to element in string and i’m comparing to length of list).. Trying to resolve that tomorrow morning. Appologies for the stupid error but i would appreciate any bits of learning.

I’m trying to combine two lists into a single list.

 m = [1,2,3]
 n = [4,5,6]
 v = m+n

 def myFun():
   return [(str(x)+str(y)) for x in m if x < len(m) for y in n if y < len(n)]

 print(myFun())

the result of myFun() should display “14, 25, 36”

i also tried to breakdown the code into a more pythonic world and have seen where i’ve gone astray:

 def my(fun()):
   for x in m if x < len(m):
     for y in n if y < len(n): # problem here, running until count 9 instead of 3
                               # like it's supposed to.. author error.. 
       newlist.append(str(x)+str(y))
   print(newlist)

Am i even headed in the right direction or should i be trying to build a map, i’ve seen a few pages saying that maps could be counter-productive if you have to reverse with a list-comp or lambda? Also, is it possible to count a specific object inside a list comprehension / lambda? (e.g. list length)?

Answer 1

use zip():

In [8]: m = [1,2,3]

In [9]: n = [4,5,6]

In [10]: [str(x)+str(y) for x,y in zip(m,n)]
Out[10]: ['14', '25', '36']

or use itertools.izip_longest() if the lists are of different lengths:

In [2]: m=[1,2,3]

In [3]: n=[4,5,6,7]

In [4]: from itertools import izip_longest

In [5]: [str(x)+str(y) for x,y in izip_longest(m,n,fillvalue="")]
Out[5]: ['14', '25', '36', '7']