Write a function that takes, as an argument, a list, identified by the variable aList. If the list only contains elements containing digits (either as strings as non-negative integers), return the string formed by concatenating all of the elements in the list (see the example that follows).

The function is as follows:

def concList(aList):

   retList = ""

   for i in aList:

       if(str(i).isdigit()):

           retList+=str(i)

       else:

           retList = "Not digits"

           break;

   return retList

Explanation:

This defines the function

def concList(aList):

This initializes the return string to an empty string

   retList = ""

This iterates through aList

   for i in aList:

This converts each element of the list to an empty list and checks if the string is digit

       if(str(i).isdigit()):

If yes, the element is concatenated

           retList+=str(i)

If otherwise

       else:

The return string is set to "No digits"

           retList = "Not digits"

And the loop is exited

           break;

This returns the return string

   return retList