Project: Calculator

Write a calculator program. A minimal calculator will support the following functions:

  • numbers with decimals (not just integers)

  • addition (1 + 2 is 3)

  • subtraction (12 - 4 is 8)

  • multiplication (33 * 2 is 66)

  • division (3 / 8 is 0.375)

  • exponents (2 ^ 3 is 8)

  • error messages when you do something wrong

Name your file calculator.py

Your calculator should keep on running until explicitly told to quit. I suggest typing a zero as the first operand to cause it to quit, i.e.

>2 + 3
5
>4 * 9
36
>0 + 2
Bye, now.

Programs may support other features if desired. Suggested other functions to add include:

  • modulus (10 % 3 is 1)

  • factorials (4 ! is 432*1, a.k.a. 24)

  • trigonometric functions (sin,cos,tan)

  • square roots

  • negation (- -3 is 3)

  • angles in degrees or radians

  • a help feature to display legal syntax and supported functions

  • previous result used as first operand

  • the ability to store and recall results

  • rounding

  • logarithms

  • arbitrary roots

  • conversion from base 10 to binary (for integers only)

Some students may wonder how to deal with the first operand possibly being a character or a number. That is, how can your program support phrases like "2 + 3" (float str flost) and "sin 30" (str float) at the same time? Well, if you read in everything as a str, then there are some python string methods that may be useful to you.

>>> "56".isdigit()
True
>>> "hello".isdigit()
False
>>> "hello".isalpha()
True

Checking float numbers is a bit more tricky. Use this function:

def isfloat(s: str) -> bool:
    """Checks if a string contains exclusively a float number.
    
    Note: if the string contains an integer,
    this function will return False.

    Args:
        s: the string to check
    
    Returns:
        True if the string exclusively contains a float.
        False otherwise.
    """
    try:
        assert s.isdigit() is False
        float(s)
    except (ValueError, AssertionError):
        return False
    else:
        return True

What to avoid

Any program which presents me with a screen like the following will not receive a very good score.

Enter the function you wish to perform.
1) addition
2) subtraction
3) multiplication
4) division
5) quit
Your choice:

Also, the same fate applies to any program that ever presents me with the following message:

 Would you like to calculate again? (y/n)

For some extra points, re-use as many functions as possible. For example, multiplication is really only addition but done multiple times.

©2021 Daniel Gallo

This assignment is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Creative Commons License

Adapted for Python from Graham Mitchell’s Programming By Doing