Introducing new variables using a given string

Question

I have a list of names my_names = ["A","B","C"] I have a function that can takes each name from a list and returns several lists of information for that name.

def my_function(name):
    return list1, list2, list3

For each name list1, list2, list3 are different.

I want to write a function that wouldn't need any user input but would return a list with 3 lists inside.

def my_function():
    for name in my_list:
        # Part I don't know how to do
        name_list = list1, list2, list3
        # A_list for "A", B_list for "B", C_list for "C"

    return A_list, B_list, C_list

The only thin I don't know is how to make python introduce new empty lists depending on the name in my_list

Possible duplicate of How do I do variable variables in Python? — Morgan Thrapp
– Morgan Thrapp, Commented Oct 19, 2015 at 19:11
You will find many posts on this topic. If you really want to stick with this solution, you can use eval or exec but it is highly recommended to not do that. Use a dictionary ! — Moritz
– Moritz, Commented Oct 19, 2015 at 19:11
I agree a dictionary is best. But you can have a list of lists if you want. Just make a main list: name_list = [] than append each list to it: name_list.append(list1), etc. Then reference each list using its index, then the elements in that list with a secondary index — Bob Dylan
– Bob Dylan, Commented Oct 19, 2015 at 19:19

Bob Dylan · Accepted Answer · 2015-10-19 21:24:51Z

2

A dictionary is best, but you can have a list of lists. Just make a main list: name_list = [] then append each list to it: name_list.append(list1), etc. Then reference each list using its index, then the elements in that list with a secondary index. For example,

def my_function():
    for name in my_list:
        name_list = []
        name_list.append(list1)
        name_list.append(list2)
        name_list.append(list3)
    return name_list

Then if you want to access the second element in the first list from the returned function, you would do so like:

name_list[0][1]

It's hard to say more without knowing more about your problem, but this will work, it's just not optimal.

edited Oct 19, 2015 at 21:24

answered Oct 19, 2015 at 19:22

Bob Dylan

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user1749431 · Accepted Answer · 2015-10-19 19:42:57Z

0

You can create a nested list with n numbers of sublists, where n is any given number of lists

n = 3
nested_list = [[]] * n
# returns [[],[],[]]
#function that takes n, n=3
def create_nested_list(n):
      nested_list = [[]] * n
      return nested_list
nested list = create_nested_list(n)

You can append items in the nested list's lists by indexing, for instancce nested_list[0]=["A"] will append the number "A" to the first sublist, nested_list[1]=["B"]to the second and nested_list[2]=["C"] to the third sublist, so nested_list = [["A"],["B"],["C"]]

edited Oct 19, 2015 at 19:42

answered Oct 19, 2015 at 19:32

user1749431

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