Why does remove(x) not work?

Question

I've tried to make a simple function, that tosses coin n times, fifty (50) times in this example, and then stores the results to the list 'my_list'. Tosses are thrown using the for loop.

If the result of the tosses are not 25 heads and 25 tails (i.e 24-26 ratio), it should erase the contents of the list my_list containing the results and loop 50 tosses again until the results are exactly 25-25.

Function:

Print the empty list.
Start the while-loop which only ends, if my_list.count(1) is 25.
Toss the coin using random(1,2).
Input results to my_list.
If my_list.count(1) is not exactly 25, then the code should erase the contents of the list and repeat the while loop.

-- coding: latin-1 --

import random
def coin_tosser():
    my_list = []

    # check if there is more or less 1 (heads) in the list
    # if there is more or less number ones in the list, loop
    # "while". If "coin tosser" throws exactly 25 heads and
    # 25 tails, then "while my_list.count(1) != 25:" turns True

    while my_list.count(1) != 25: # check if there is more or less 1 (heads) in the list
        print "Throwing heads and tails:"
        for i in range(50):
            toss = random.randint(int(1),int(2)) #tried this also without int() = (1,2)
            my_list.append(toss)
        if my_list.count(1) < 25 or my_list.count(1) > 25:
            my_list.remove(1) # remove number ones (heads) from the list
            my_list.remove(2) # remove number twos (tails) from the list

    # after loop is finished (25 number ones in the list), print following:

    print "Heads is in the list",
    print my_list.count(1), "times."
    print "Tails is in the list",
    print my_list.count(2), "times."
    # print
    print my_list

coin_tosser()

Problem

When I try to use my_list.remove(1), it doesn't remove anything from the list. If I replace my_list.remove(1) with my_list.remove('test') and add 'test' to my_list, then the program removes 'test', if conditions is not met (as it should).

Why it doesn't remove numbers? I'm not sure if these "1" and "2" are stored to list as int or as str. My guess is that in str

What have I done wrong?

http://stackoverflow.com/questions/18418/elegant-way-to-remove-items-from-sequence-in-python — Avinash Babu, Oct 12 '14 at 15:47
Instead of removing the numbers from the old list, why not just make a new one? (`my_list = []` inside the `if`) — parchment, Oct 12 '14 at 15:49
this doen't anwser my question. Why my_list.remove() can't remove numeric str like my_list.remove(1) but it will remove "test" — Kasperi Koski, Oct 12 '14 at 16:08

poke · Answer 1 · 2014-10-12T16:36:50.510

list.remove(x) only removes the first item which equals to x, so you are only removing a single item each time with this:

my_list.remove(1)
my_list.remove(2)

As such, you don’t clear your list at all. Instead, you can just clear the list completely, by setting it to a new empty list:

my_list = []

Since you are only interested in the number of head/tails throws, you can also just count them instead of remembering all individual tosses. So you’d just have a counter:

headCount = 0
while headCount != 25:
    print "Throwing heads and tails:"
    headCount = 0
    for i in range(50):
        toss = random.randint(1, 2)
        if toss == 1:
            headCount += 1

I would correct that `list.remove(x)` only removes the first item, instead of returns — dreyescat, Oct 12 '14 at 16:13

score 0 · Accepted Answer · answered Oct 12 '14 at 16:09

As @poke stated, list.remove(x) only removes the first appearance of x in list. I would simply use a new my_list list in every iteration and get rid of the entire if inside the loop.

while my_list.count(1) != 25: # check if there is more or less 1 (heads) in the list
    print "Throwing heads and tails:"
    my_list = []
    for i in range(50):
        toss = random.randint(int(1),int(2)) #tried this also without int() = (1,2)
        my_list.append(toss)

You don't need to check again if you have 25 heads inside the loop because you are just checking it in the loop condition while my_list.count(1) != 25

BTW:

my_list.count(1) < 25 or my_list.count(1) > 25

is the same as your while condition but less readable.

Thank you dreyescat and @poke! – Kasperi Koski Oct 12 '14 at 19:49 — Kasperi Koski, Oct 12 '14 at 19:49

Why does remove(x) not work?

Function:

Problem

2 Answers2