calculator.py

"""
Written by  : Shreyas Daniel - github.com/shreydan
Description : Uses Pythons eval() function
              as a way to implement calculator.
             
Functions available are:
--------------------------------------------
                         + : addition
                         - : subtraction
                         * : multiplication
                         / : division
                         % : percentage
                         e : 2.718281...
                        pi : 3.141592... 
                      sine : sin(rad)
                    cosine : cos(rad)
                   exponent: x^y
                   tangent : tan(rad)
                 remainder : XmodY
               square root : sqrt(n)
  round to nearest integer : round(n)
convert degrees to radians : rad(deg)
absolute value             : aval(n)
"""

import sys

## Imported math library to run sin(), cos(), tan() and other such functions in the calculator

from fileinfo import raw_input


def calc(term):
    """
    input: term of type str
    output: returns the result of the computed term.
    purpose: This function is the actual calculator and the heart of the application
    """

    # This part is for reading and converting function expressions.
    term = term.lower()

    # This part is for reading and converting arithmetic terms.
    term = term.replace(" ", "")
    term = term.replace("^", "**")
    term = term.replace("=", "")
    term = term.replace("?", "")
    term = term.replace("%", "/100.00")
    term = term.replace("rad", "radians")
    term = term.replace("mod", "%")
    term = term.replace("aval", "abs")

    functions = [
        "sin",
        "cos",
        "tan",
        "pow",
        "cosh",
        "sinh",
        "tanh",
        "sqrt",
        "pi",
        "radians",
        "e",
    ]

    for func in functions:
        if func in term:
            withmath = "math." + func
            term = term.replace(func, withmath)

    try:

        # here goes the actual evaluating.
        term = eval(term)

    # here goes to the error cases.
    except ZeroDivisionError:

        print("Can't divide by 0.  Please try again.")

    except NameError:

        print("Invalid input.  Please try again")

    except AttributeError:

        print("Please check usage method and try again.")
    except TypeError:
        print("please enter inputs of correct datatype ")

    return term


def result(term):
    """
    input:  term of type str
    output: none
    purpose: passes the argument to the function calc(...) and
            prints the result onto console.
    """
    print("\n" + str(calc(term)))


def main():
    """
    main-program
    purpose: handles user input and prints
             information to the console.
    """

    print(
        "\nScientific Calculator\n\nFor Example: sin(rad(90)) + 50% * (sqrt(16)) + round(1.42^2)"
        + "- 12mod3\n\nEnter quit to exit"
    )

    if sys.version_info.major >= 3:
        while True:
            k = input("\nWhat is ")
            if k == "quit":
                break
            result(k)

    else:
        while True:
            k = raw_input("\nWhat is ")
            if k == "quit":
                break
            result(k)


if __name__ == "__main__":
    main()