[FIXED] Is there a nicer way to split a user input at a specific character, add everything before it to a list, then the character, then continue repeating?

Issue

I'm trying to create a "math interpreter" just for fun. So first step should probably be converting user input into a format I can easily work with. Now, I got it working, it's splitting everything as expected, but I have a feeling that there's a much much much more simple way of doing it. Here's what I have:

Main function:

def main():

    userInput:str = input("What problem would you like solved?\nProblem: ")

    str_build:str = ""
    problem_list:list = []

    index:int = 0

    while(index < len(userInput)):
        curr_char:str = userInput[index]

        if checkForSign(curr_char) == False:
            str_build += curr_char
        else:

            if str_build != "":
                problem_list.append(str_build)

            problem_list.append(curr_char)
            str_build = ""

        index += 1

    print(problem_list)

    return 0

And the one that checks for operands:

def checkForSign(character: str) -> bool:
    match character:
        case "+":
            return True
        case "-":
            return True
        case "/":
            return True
        case "*":
            return True
        case _:
            return False

So lets say the user inputs 10+2*5-534/2

Then the preferred output should be ['10', '+', '2', '*', '5', '-', '534', '/', '2']

So far I've tried regex (not much success there, but I was curios about it). Code works, I do get a nicer arrangement of the inputs, but there has to be a shorter, maybe more efficient way of doing it.

Edit: Atm it can't really do anything when it's presented with a negative number, so preferably I'd like to be able to work with those too.

Solution

If your input is solely concerned with positive integers then:

ui = input("What problem would you like solved? ")

result = [""]

for c in ui:
    if c.isdecimal():
        result[-1] += c
    elif c in "+-*/":
        result.extend([c, ""])
    else:
        print("Invalid formula")
        break
else:
    print(result)

For an input of 10+2*5-534/2 this will output:

['10', '+', '2', '*', '5', '-', '534', '/', '2']

Answered By - CtrlZ