iteration with map() function

Question

I am trying to use the map() function and capitalize all the words in the list.

my_pets = ['sisi', 'bibi', 'titi', 'carla']

def capitalizing(a):
    for item in a:
        b = item.upper()
        return b

print(list(map(capitalizing, my_pets)))

If I run this code, I get the output as following:

['S', 'B', 'T', 'C']

Why is that? Why does the code just runs the first letter and stops for each word?

I already know that the "for" loop/iteration is incorrect to get all the words, I don't need it, but why is this loop runs for the first letter of each word?

Thanks for your assistance in advance.

Answer 1

Your placement of return inside the for loop, causes it to return after the first iteration (on the first character of the string passed to capitalizing). eg:
capitalizing('sisi')

for item in a:     # a = 'sisi'
  b = item.upper() # item = 's', b = 'S'
  return b         # b = 'S', return 'S' and exit function

The code can be written more concisely, as the other answers have shown. This code is doing things redundantly.

Here is a fixed version of your code, to return after the for loop is finished building the string, and not after the first iteration:

my_pets = ['sisi', 'bibi', 'titi', 'carla']

def capitalizing(a):
    b = ""
    for item in a:
        b += item.upper()
        # using return here will exit the function immediately after the first iteration
    return b # return after finishing

print(list(map(capitalizing, my_pets)))