How to mutate a list with a function in python?

Question

Here\'s a pseudocode I\'ve written describing my problem:-

func(s):
   #returns a value of s

x = a list of strings
print func(x)
print x #these two should          


        

Answer 1

That's already how it behaves, the function can mutate the list

>>> l = ['a', 'b', 'c'] # your list of strings
>>> def add_something(x): x.append('d')
...
>>> add_something(l)
>>> l
['a', 'b', 'c', 'd']

Note however that you cannot mutate the original list in this manner

def modify(x):
    x = ['something']

(The above will assign x but not the original list l)

If you want to place a new list in your list, you'll need something like:

def modify(x):
    x[:] = ['something']