Performing calculations with updated integer

Question

How could I improve this code to make it shorter and more functional?

#!usr/bin/python
import time
integer = 0
print("The current integer is set at " + str(integer) + ".")
print("\n")
time.sleep(2)
prompt = raw_input("Would you like to change the integer? (Y/N) ")
print("\n")
if prompt == 'y':
    integer = int(raw_input("Insert the new integer here: "))
    print("\n")
    print("You have changed the integer to " + str(integer) + ".")
    print("\n")
    print("\n")
    time.sleep(1)
    print("1. Add / 2. Subtract / 3. Multiply / 4. Divide")
    print("\n")
    new_int = raw_input("What would you like to do with your new integer? (Choose a number) ")
    print("\n")
    if new_int == '1':
        added_int = int(raw_input("What number would you like to add to your integer (" + str(integer) + ") by?"))
        outcome1 = integer + added_int
        print("\n")
        print("The sum of " + str(integer) + " + " + str(added_int) + " is " + str(outcome1))
    if new_int == '2':
        subtracted_int = int(raw_input("What number would you like to subtract your integer (" + str(integer) + ") by?"))
        outcome2 = integer - subtracted_int
        print("\n")
        print("The difference of " + str(integer) + " - " + str(subtracted_int) + " is " + str(outcome2))
    if new_int == '3':
        multiplied_int = int(raw_input("What number would you like to multiply your integer (" + str(integer) + ") by?"))
        outcome3 = integer * multiplied_int
        print("\n")
        print("The product of " + str(integer) + " x " + str(multiplied_int) + " is " + str(outcome3))
    if new_int == '4':
        divided_int = int(raw_input("What number would you like to divide your integer (" + str(integer) + ") by?"))
        outcome4 = integer / divided_int
        print("\n")
        print("The quotient of " + str(integer) + " / " + str(divided_int) + " is " + str(outcome4))
elif prompt == "n":
    print("The integer will stay the same.")
    time.sleep(2)
    print("Press any key to exit...")
else:
    print("Invalid input.")
raw_input()

Answer 1

How about something like this?

import time

def add_num(x):
    added_int = int(raw_input("What number would you like to add to your integer (%s) by?" % x))
    outcome = x + added_int
    print("\nThe sum of %s + %s is %s" % (x, added_int, outcome))
    return outcome

def sub_num(x):
    sub_int = int(raw_input("What number would you like to subtract to your integer (%s) by?" % x))
    outcome = x - sub_int
    print("\nThe subtract of %s - %s is %s" % (x, added_int, outcome))
    return outcome

def mul_num(x):
    mul_int = int(raw_input("What number would you like to multiply your integer (%s) by?" % x))
    outcome = x * mul_int
    print("\nThe multiplication of %s * %s is %s" % (x, added_int, outcome))
    return outcome

def div_num(x):
    div_num = int(raw_input("What number would you like to divide your integer (%s) by?" % x))
    outcome = x / float(div_num)
    print("\nThe divider of %s / %s is %s" % (x, added_int, outcome))
    return outcome

def main():
    op_map = {"1":add_num, "2":sub_num, "3":mul_num, "4":div_num}
    number = 0
    print("The current integer is set at %s ." % number)
    while True:
        prompt = raw_input("Would you like to change the number? (Y/N)").lower()
        if prompt == "y":
            number = int(raw_input("Insert the new integer here: "))
            print("\nYou have changed the integer to %s .\n\n" % number)
            time.sleep(1)
            print("1. Add / 2. Subtract / 3. Multiply / 4. Divide\n")

            op = raw_input("What would you like to do with your new integer? (Choose a number) \n")
            if op is not None:
                operation = op_map.get(op)
                number = operation(number)

        elif prompt == "n":
            print("The integer will stay the same.")
            time.sleep(2)
            raw_input("Press enter key to exit...")
            break
        else:
            print("Invalid response")

if __name__ == '__main__':
    main()

Answer 2

Here is a less verbose script that does the basic operations like you are doing. It may be a little advanced for you based on what you wrote, but I thought you might be interested in having a look.

import re

pat = re.compile(r'\s*(\-?\d+\.?\d*)\s*([+-/*])\s*(\-?\d+\.?\d*)\s*')

while True:
    print 'Input a basic expression (ex: 12 * 4, 3.24+3, 19/2, etc) or -1 to exit:'
    user_input = raw_input()
    if user_input == '-1':
        break

    m = pat.match(user_input)
    if m:
        try:
            result = eval(m.group())
        except ZeroDivisionError:
            print 'Cannot divide by zero.',
            continue

        print m.group(1), m.group(2), m.group(3), '=', result
    else:
        print 'Invalid expression.',

Sample Output from running the script:

>>>Input a basic expression (ex: 12 * 4, 3.24+3, 19/2, etc) or -1 to exit:
-2 * 1
-2 * 1 = -2
Input a basic expression (ex: 12 * 4, 3.24+3, 19/2, etc) or -1 to exit:
-4 / 0
Cannot divide by zero. Input a basic expression (ex: 12 * 4, 3.24+3, 19/2, etc) or -1 to exit:
5 /2
5 / 2 = 2
Input a basic expression (ex: 12 * 4, 3.24+3, 19/2, etc) or -1 to exit:
5/2.0
5 / 2.0 = 2.5
Input a basic expression (ex: 12 * 4, 3.24+3, 19/2, etc) or -1 to exit:
78--2
78 - -2 = 80
Input a basic expression (ex: 12 * 4, 3.24+3, 19/2, etc) or -1 to exit:
90+2
90 + 2 = 92
Input a basic expression (ex: 12 * 4, 3.24+3, 19/2, etc) or -1 to exit:
-1
>>>

Here's a little breakdown in case you don't understand what's going on. The script uses regular expressions, hence import re, to extract a simple equation. A simple equation meaning a number followed by an operation followed by another number.

'\s*(\-?\d+\.?\d*)\s*([+-/*])\s*(\-?\d+\.?\d*)\s*'

is the regular expression.

\s* means 0 or more spaces
\-? means there may or may not be a - (for negative numbers)
\d+ means 1 or more digits
\.? means there may or may not be a . (for decimal numbers)
\d* means 0 or more digits
[+-/*] means one of those symbols

So lets look at what is being grouped in the brackets ()

(\-?\d+\.?\d*) which means a positive or negative number that could be an integer or a decimal
([+-/*]) which picks the operation to be performed on the numbers
(\-?\d+\.?\d*) which is the same as the first

Each of these expressions in brackets are separated with a \s* and since match(string) only keeps what's in the brackets, all the spacing is ignored.

The regular expression is then compiled and you can use that pattern variable (which I called pat) to match against input (which I stored in m in the line m = pat.match(user_input)).

As I said above, match only keeps what's in the brackets, and it puts them into groups.

m.group(0) #is everything ex) 10*10.5
m.group(1) #is the first brackets contents. ex) 10
m.group(2) #is the second brackets contents. ex) *
m.group(3) #is the third brackets contents. ex) 10.5 

You can see how I printed out the equation with the result using m.group(). Also, I should say that when match(input) doesn't find a match, it returns None so if m: in the code passes if a match is found and fails if one isn't.

Finally, eval() will evaluate the expression inside of it which is how we get the result.

You can also see that I used a try/except statement to catch division by zero. Oh and if you put an r in front of a string like r'hello world\n', it is a "raw string" and ignores escaped characters (ie: things like new line \n) and just stores the characters as is.

Even if this isn't exactly what you were looking for, I hope you found it interesting and perhaps learned something from it.

Answer 3

@Jackob wrote a better solution, but I can still see much duplication, here you can see a DRY version using higher order functions:

def user_interface_operation(start, operation):
    b = int(raw_input("What is x in {} {} x ?".format(start, operation.__name__)))
    outcome = operation(start, b)
    print("The result is {}".format(outcome))
    return outcome

add_num = lambda start: user_interface_operation(start, op.add)
sub_num = lambda start: user_interface_operation(start, op.sub)
mul_num = lambda start: user_interface_operation(start, op.mul)
div_num = lambda start: user_interface_operation(start, op.div)