issue adding result from random.choice to an empty list in a class

Question

I am issue understanding an output for the following code I wrote for a school assignment.

class Number:

  def __init__(self):

    self.__number = []

 

  def pick_num(self, my_list):

    x = random.choice(my_list)

    self.__number = self.__number.append(x)
  
    return print("Here's your list with the added number: ", self.__number)

def main()

    random_number = Number()

    my_list = [1, 2, 3, 4]

    random_number.pick_num(my_list)

main()

output

Here's your list with the added number: None

I don't understand why I get None instead of the desired output [n]

`append()` does not return anything so `self.__number = self.__number.append(x)` sets `self.__number` to `None` — Mark, Apr 20 '21 at 18:22

score 2 · Accepted Answer · answered Apr 20 '21 at 18:23

2

import random

class Number:

    def __init__(self):
        self.__number = []

    def pick_num(self, my_list):
        x = random.choice(my_list)

        self.__number.append(x)

        return print("Here's your list with the added number: ", self.__number)


def main():

    random_number = Number()

    my_list = [1, 2, 3, 4]

    random_number.pick_num(my_list)


main()

.append returns None and modifies the list it's called upon.

answered Apr 20 '21 at 18:23

Vulwsztyn

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Brilliant, saw where my mistake was. Thanks a lot @Vulwsztyn – AwesomePossum Apr 20 '21 at 18:28

issue adding result from random.choice to an empty list in a class

1 Answers1