Why is my simple prime number checker not working?

I have made changes to my code which helped the size but still get the error

IndexError: list index out of range

But I cannot seem to find out why. I know it has to do with [-1] but I can't seem to figure out why it isn't calling the last listed element.

number = 4
not_primes = 0
primes = []
while 1:
    for i in range(2, number):
        if number % i == 0:
            i = not_primes
        else:
            primes.append(number)
        print(primes[-1])
        number += 1

Solution

try this code (with little change on your code):

current_number = 2
not_prime = list()
prime_numbers = list()

def odd_checker():    
    if current_number % 2 == 0 and current_number != 2:
        not_prime.append(current_number)
    else:
        last_digit_check()

def last_digit_check():
    if current_number % 5 == 0 and current_number != 5:
        not_prime.append(current_number)
    else:
        last_prime_checker(current_number)

def last_prime_checker(the_number):
    for i in prime_numbers: 
        if the_number % i == 0:
            not_prime.append(the_number)
            return
    prime_numbers.append(the_number)

while True:
    odd_checker()
    current_number += 1
    print(prime_numbers)
    
    y_n = input('do you continue(y/n) : ') if current_number % 10 == 0 else ''
    if y_n == 'n':
        break

output:

[2]
[2, 3]
[2, 3]
[2, 3, 5]
[2, 3, 5]
[2, 3, 5, 7]
[2, 3, 5, 7]
[2, 3, 5, 7]
do you continue(y/n) : y
[2, 3, 5, 7]
[2, 3, 5, 7, 11]
[2, 3, 5, 7, 11]
[2, 3, 5, 7, 11, 13]
[2, 3, 5, 7, 11, 13]
[2, 3, 5, 7, 11, 13]
[2, 3, 5, 7, 11, 13]
[2, 3, 5, 7, 11, 13, 17]
[2, 3, 5, 7, 11, 13, 17]
[2, 3, 5, 7, 11, 13, 17, 19]
do you continue(y/n) : y
[2, 3, 5, 7, 11, 13, 17, 19]
[2, 3, 5, 7, 11, 13, 17, 19]
[2, 3, 5, 7, 11, 13, 17, 19]
[2, 3, 5, 7, 11, 13, 17, 19, 23]
[2, 3, 5, 7, 11, 13, 17, 19, 23]
[2, 3, 5, 7, 11, 13, 17, 19, 23]
[2, 3, 5, 7, 11, 13, 17, 19, 23]
[2, 3, 5, 7, 11, 13, 17, 19, 23]
[2, 3, 5, 7, 11, 13, 17, 19, 23]
[2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
do you continue(y/n) : n

EDIT : Adding new code for finding prime the number as request on comment.

number = 4
not_primes = False
primes = []
while 1:
    
    for i in range(2, number):
        if number % i == 0:
            not_prime = True
    
    if not_prime == False:
        primes.append(number)
        
        
    try:
        print(primes[-1])
    except:
        print('do not find prime yet')
        
        
    number += 1
    not_prime = False
    
    y_n = input('do you continue(y/n) : ') if number % 10 == 0 else ''
    if y_n == 'n':
        break

output:

do not find prime yet
5
5
7
7
7
do you continue(y/n) : y
7
11
11
13
13
13
13
17
17
19
do you continue(y/n) : y
19
19
19
23
23
23
23
23
23
29
do you continue(y/n) : n