Simple Python Calculator

Question

Hi I am new to python and I am practicing by making a simple calculator. The program lets me input numerical values for meal, tax, and tip but when doing the calculation I get this error:

Traceback (most recent call last):
  File "C:/Users/chacha04231991/Desktop/pytuts/mealcost.py", line 5, in <module>
    meal = meal + meal * tax
TypeError: can't multiply sequence by non-int of type 'str'

The is the code:

meal = raw_input('Enter meal cost: ')
tax = raw_input('Enter tax price in decimal #: ')
tip = raw_input('Enter tip amount in decimal #: ')

meal = meal + meal * tax
meal = meal + meal * tip

total = meal
print 'your meal total is ', total

result of the `raw_input` is `str`. – alexvassel Dec 20 '12 at 10:41 — alexvassel, Dec 20 '12 at 10:41

score 1 · Accepted Answer · answered Dec 20 '12 at 10:41

1

You need to convert your inputs from strings to numbers, e.g. integers:

meal = int(raw_input('Enter meal cost: '))
tax = int(raw_input('Enter tax price in decimal #: '))
tip = int(raw_input('Enter tip amount in decimal #: '))

You could also use the decimal type if you need to enter fractional monetary amounts.

from decimal import Decimal 
meal = Decimal(raw_input('Enter meal cost: '))
tax = Decimal(raw_input('Enter tax price in decimal #: '))
tip = Decimal(raw_input('Enter tip amount in decimal #: '))

I would advise you not to use floats for this because it will give rounding errors.

answered Dec 20 '12 at 10:41

Mark Byers

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It works fine using float but when I try decimal is gives this error: Traceback (most recent call last): File "C:/Users/chacha04231991/Desktop/pytuts/mealcost.py", line 4, in tax = decimal(raw_input('Enter tax price in decimal #: ')) NameError: name 'decimal' is not defined – codeYah Dec 20 '12 at 11:05
@codeYah: `decimal` with a small `d` is the name of the module. The type `Decimal` has a capital `D`. – Mark Byers Dec 20 '12 at 11:49

score 1 · Answer 2 · answered Dec 20 '12 at 10:42

when you use raw_input, the input you get is of type str

>>> meal = raw_input('Enter meal cost: ')
Enter meal cost: 5
>>> type(meal)
<type 'str'>

you should convert it to int/float before performing action

>>> meal = int(raw_input('Enter meal cost: '))
Enter meal cost: 5
>>> type(meal)
<type 'int'>

score 0 · Answer 3 · edited May 23 '17 at 12:27

0

Input is a string by default in python. You will have to convert it to an integer before multiplying.

int(meal)
int(tax)
int(tip)

should do the trick.

Parse String to Float or Int

edited May 23 '17 at 12:27

Community

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answered Dec 20 '12 at 10:44

iOSAndroidWindowsMobileAppsDev

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score 0 · Answer 4 · answered Dec 30 '18 at 04:15

This is simple and also I wrote this code depending on the user operand input as string..

def calculator(a, b, operand):
    result = 0
    if operand is '+':
      result = a + b
    elif operand is '-':
      result = a - b
    elif operand is '*':
      result = a * b
    elif operand is '/':
      result = a / b
    return result

calculator(2, 3, '+')
output -> 5

score -1 · Answer 5 · answered Jun 04 '22 at 07:56

-1

By default, python assumes all input as string value. So we need to convert string values to numbers through either float or int.

answered Jun 04 '22 at 07:56

sudip paudel

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This has already been mentioned in the other answers. – Eric Aya Jun 04 '22 at 12:29

Simple Python Calculator

5 Answers5