CODEWITHSUNDEEP
pythonpython-3.xalgorithm
kabir singh
kabir singh

Reputation: 13

How to calculate negative numbers on calculator problem using python3?

I have written a basic program to do arithmetic operations, where the user input will be in a single line containing two integers and operator(+, -, *, /, and %) similar to 3 + 5. I have written this code so far it works for all positive integers but when I try to give a negative integer it throws IndexError

def calculator(given_input):
    cal = []
    
    def operation(given_input):
        int_input = given_input.split()
        for i in int_input:
            if i.isdigit():
                cal.append(int(i))

    #for addition            
    if ("+" in given_input):
        operation(given_input)
        print(cal[0] + cal[1])
    #for subraction
    if ("-" in given_input):
        operation(given_input)
        print(cal[0] - cal[1])
    #for division
    if ("/" in given_input):
        operation(given_input)
        print(cal[0] - cal[1])
    #for multiplication
    if ("*" in given_input):
        operation(given_input)
        print(cal[0] * cal[1])
    #for modulous
    if ("%" in given_input):
        operation(given_input)
        print(cal[0] % cal[1])
    
        
given_input = input()
calculator(given_input)

Upvotes: 0

Views: 377

Answers (1)

azro
azro

Reputation: 54148

From the supposition you make that each element is space-separated, (not like 3+4) as you used given_input.split() that splits on space, you can directly use the index of that element. Also don't call operation in each branch, call it before or better just execute the code directly

def calculator(given_input):
    cal = []

    int_input = given_input.split()
    cal.append(int(int_input[0]))
    cal.append(int(int_input[2]))

    if "+" == int_input[1]:
        print(cal[0] + cal[1])
    elif "-" == int_input[1]:
        print(cal[0] - cal[1])
    elif "/" == int_input[1]:
        print(cal[0] - cal[1])
    elif "*" == int_input[1]:
        print(cal[0] * cal[1])
    elif "%" == int_input[1]:
        print(cal[0] % cal[1])

To handle multiple situations, with spaced or non-spaced content, use a regular expression with re module, a regex like (-?\d+)\s*([+-/*%])\s*(-?\d+)

  • (-?\d+) a possible minus, then an amount of digit
  • \s* a posible amount of spaces
  • ([+-/*%]) any char in these 5 +-/*%
  • \s* a posible amount of spaces
  • (-?\d+) a possible minus, then an amount of digit
import re

def calculator(given_input):
    int_input = re.search("(-?\d+)\s*([+-/*%])\s*(-?\d+)", given_input)
    if not int_input:
        print("Format error of '", int_input, "'")
        return

    a, operator, b = int_input.groups()
    a, b = int(a), int(b)

    if "+" == operator:
        print(a + b)
    elif "-" == operator:
        print(a - b)
    elif "/" == operator:
        print(a / b)
    elif "*" == operator:
        print(a * b)
    elif "%" == operator:
        print(a % b)

Upvotes: 2

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