2

lets say i have a list of random numbers

randomlist = [9, 8, 18, 1, 17, 3, 13, 4, 13, 1, 9, 10, 7, 13, 3, 9, 13, 10, 18, 10, 19, 3, 14, 14, 19, 4, 20, 17, 8, 17, 3, 12, 8, 12, 1, 2, 15, 13, 2, 8, 18, 10, 14, 11, 17, 11, 2, 7, 4, 7, 5, 5, 18, 7, 11, 13, 20, 9, 2, 14, 19, 1, 16, 10, 16, 19, 13, 19, 11, 17, 8, 2, 10, 16, 5, 14, 7, 11, 17, 9, 9, 6, 12, 6, 12, 4, 14, 10, 2, 6, 9, 1, 14, 4, 14, 13, 18, 13, 6, 8]

There are three categorys of numbers: numbers which are divisible by two (2,4,6,8,10,12,14,16,18,20) prime numbers except two (3,7,11,13,17,19) rest (1,5,9,15)

Now what i want to do is the following: I will go through the list and whenever a number of the rest category occurs i want to create a list like this [ %2 , prime] whereas the elements are the ones which occured most recently in the list. The goal is to have a lists of lists with two elements. I hope its clear what im trying to do. Here is my code:

randomlist = [9, 8, 18, 1, 17, 3, 13, 4, 13, 1, 9, 10, 7, 13, 3, 9, 13, 10, 18, 10, 19, 3, 14, 14, 19, 4, 20, 17, 8, 17, 3, 12, 8, 12, 1, 2, 15, 13, 2, 8, 18, 10, 14, 11, 17, 11, 2, 7, 4, 7, 5, 5, 18, 7, 11, 13, 20, 9, 2, 14, 19, 1, 16, 10, 16, 19, 13, 19, 11, 17, 8, 2, 10, 16, 5, 14, 7, 11, 17, 9, 9, 6, 12, 6, 12, 4, 14, 10, 2, 6, 9, 1, 14, 4, 14, 13, 18, 13, 6, 8]


def check_prime(x):

    for i in range(2, x):
        if (x % i) == 0:
            return False
    else:
        return True

def check_number(x):

    if x%2 == 0:
        return "zweier"

    elif check_prime(x) == True:
        return "prim"

    else:
        return "rest"

final_list = []
partial_list = [0,0]

for x in randomlist:

    if check_number(x) =="zweier":
        partial_list[0] = x

    elif check_number(x) == "rest":
        partial_list[1] = x

    else:
        final_list.append(partial_list)

for x in final_list:
    print(x)

Ouput:

[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]
[8, 9]

What confuses me very much is that if i print the final_list members right after creating them it shows the right solution:

randomlist = [9, 8, 18, 1, 17, 3, 13, 4, 13, 1, 9, 10, 7, 13, 3, 9, 13, 10, 18, 10, 19, 3, 14, 14, 19, 4, 20, 17, 8, 17, 3, 12, 8, 12, 1, 2, 15, 13, 2, 8, 18, 10, 14, 11, 17, 11, 2, 7, 4, 7, 5, 5, 18, 7, 11, 13, 20, 9, 2, 14, 19, 1, 16, 10, 16, 19, 13, 19, 11, 17, 8, 2, 10, 16, 5, 14, 7, 11, 17, 9, 9, 6, 12, 6, 12, 4, 14, 10, 2, 6, 9, 1, 14, 4, 14, 13, 18, 13, 6, 8]


def check_prime(x):
    for i in range(2, x):
        if (x % i) == 0:
            return False
    else:
        return True

def check_number(x):

    if x%2 == 0:
        return "zweier"

    elif check_prime(x) == True:
        return "prim"

    else:
        return "rest"

final_list = []
partial_list = [0,0]

for x in randomlist:

    if check_number(x) =="zweier":
        partial_list[0] = x

    elif check_number(x) == "rest":
        partial_list[1] = x

    else:
        final_list.append(partial_list)
        print(final_list[-1])

Output:

[18, 9]
[18, 9]
[18, 9]
[18, 9]
[4, 9]
[4, 9]
[10, 9]
[10, 9]
[10, 9]
[10, 9]
[10, 9]
[10, 9]
[14, 9]
[20, 9]
[8, 9]
[8, 9]
[12, 9]
[2, 15]
[14, 15]
[14, 15]
[14, 15]
[2, 15]
[4, 15]
[4, 15]
[4, 15]
[18, 15]
[18, 15]
[18, 15]
[14, 9]
[14, 9]
[16, 9]
[16, 9]
[16, 9]
[16, 9]
[16, 9]
[16, 9]
[14, 9]
[14, 9]
[14, 9]
[6, 9]
[14, 9]
[18, 9]

So it seems like the basis idea is okay. I tried very much but i just cant find out what i am doing wrong. Thanks very much for help !

GenkidamaApple
  • 21
  • 3

2 Answers2

1

The reason for this is that when you iterate over the items in your randomlist and append partial_list to final_list, what you append is a reference to the same object (partial_list), but not the values contained.

If you change the append statement to be like:

final_list.append(partial_list.copy())

Will every time append a copy of the partial_list and your code will eventually print correct result.

Therefore your code would be:

def check_prime(x):

    for i in range(2, x):
        if (x % i) == 0:
            return False
    else:
        return True

def check_number(x):

    if x%2 == 0:
        return "zweier"

    elif check_prime(x) == True:
        return "prim"

    else:
        return "rest"

final_list = []
partial_list = [0,0]

for x in randomlist:

    if check_number(x) =="zweier":
        partial_list[0] = x

    elif check_number(x) == "rest":
        partial_list[1] = x
    else:
        final_list.append(partial_list.copy())

for x in final_list:
    print(x)
C.Georgiadis
  • 201
  • 3
  • 9
1

This will give you the desired results. Refer to here that explains what is happening.

randomlist = [9, 8, 18, 1, 17, 3, 13, 4, 13, 1, 9, 10, 7, 13, 3, 9, 13, 10, 18, 10, 19, 3, 14, 14, 19, 4, 20, 17, 8, 17, 3, 12, 8, 12, 1, 2, 15, 13, 2, 8, 18, 10, 14, 11, 17, 11, 2, 7, 4, 7, 5, 5, 18, 7, 11, 13, 20, 9, 2, 14, 19, 1, 16, 10, 16, 19, 13, 19, 11, 17, 8, 2, 10, 16, 5, 14, 7, 11, 17, 9, 9, 6, 12, 6, 12, 4, 14, 10, 2, 6, 9, 1, 14, 4, 14, 13, 18, 13, 6, 8]


def check_prime(x):
    for i in range(2, x):
        if (x % i) == 0:
            return False
    else:
        return True

def check_number(x):
    if x%2 == 0:
        return "zweier"
    elif check_prime(x) == True:
        return "prim"
    else:
        return "rest"

final_list = []
partial_list = [0,0]

for x in randomlist:
    if check_number(x) =="zweier":
        partial_list[0] = x
    elif check_number(x) == "rest":
        partial_list[1] = x
    else:
        final_list.append(partial_list.copy())

for x in final_list:
    print(x)
chitown88
  • 27,527
  • 4
  • 30
  • 59