Python 3 - Calculator

Question

This is my second Python beginner program done without help. I would like to receive comments on how clean does it look and if it can be done more efficiently.

def user_operation():
 return input('Type operation: ')
def user_number():
 """Return numbers used in operations"""
 n1 = input('First number: ')
 n2 = input('Second number: ')
 return (int(n1), int(n2))
#Operations
def add(x, y):
 a = x + y
 print ('%d + %d is %d' % (x, y, a)) 
def sub(x, y):
 s = x - y
 print ('%d - %d = %d' % (x, y, s))
def mult(x, y):
 m = x * y
 print('%d * %d is %d' % (x, y, m))
def div(x, y):
 d = x / y
 print ('%d / %d is %d' % (x, y, d)) 
def calculate():
 while True:
 n1, n2 = user_number() 
 operation = user_operation()
 if operation.lower() == 'quit':
 return False
 elif operation == '1':
 add(n1, n2)
 elif operation == '2':
 sub(n1, n2) 
 elif operation == '3':
 mult(n1, n2) 
 elif operation == '4':
 div(n1, n2)
 else:
 print ("That is not an operation!!") 
def main():
 print ("Calculator program by Jfelix\n"
 "Available operations:\n1.Addition\n2.Subtraction\n3.Multiplication\n4.Division\n"
 "Type their respective number to perform the selected operation\n"
 "If done with an operation, type 'back'\n"
 "Type 'quit' to end the program.\n"
 )
 calculate()
if __name__ == "__main__":
 main()

• ChatterOne: The division operation is missing its arguments, which means that technically the code is not ready for review (because the code is not working)... But since you're a beginner that's showing some effort, I'm sure a review is coming anyway :-)
• Billal BEGUERADJ: That is a typo. @ChatterOne
• Graipher: Since you have not received an answer yet, you can still fix it, though.

Answer 1

Nice first project! It is generally better practice to have functions return values instead of printing them. I added a power function to yours and made it more user friendly by having them type the symbol instead of a number.also you should add square, cube and other roots making the symbol '//'. otherwise it looks good, your code is nicely formatted and looks great.

def user_operation():
 return input('Type operation: ')
def user_number():
 #Return numbers used in operations
 n1 = int(input('First number: '))
 n2 = int(input('Second number: '))
 return (n1, n2)
#Operations
def add(x, y):
 a = x + y
 return ('%d + %d is %d' % (x, y, a)) 
def sub(x, y):
 s = x - y
 return ('%d - %d = %d' % (x, y, s))
def mult(x, y):
 m = x * y
 return ('%d * %d is %d' % (x, y, m))
def div(x, y):
 d = x / y
 return ('%d / %d is %d' % (x, y, d)) 
def sqr(x,y):
 d = x ** y
 return ('%d ** %d is %d' % (x, y, d)) 
def calculate():
 while True:
 n1, n2 = user_number() 
 operation = user_operation()
 if operation.lower() == 'quit':
 break
 elif operation == '+':
 print (add(n1, n2))
 elif operation == '-':
 print (sub(n1, n2)) 
 elif operation == '*':
 print (mult(n1, n2)) 
 elif operation == '/':
 print (div(n1, n2))
 elif operation == '**':
 print (sqr(n1, n2))
 else:
 print ("That is not a valid operation!!") 
def main():
 print ("Calculator program by Jfelix\n"
 "Available operations:\n1. Addition (+)\n2. Subtraction (-)\n3. Multiplication(*)\n4. Division (/)\n5. Power (**)"
 "Type their respective character(s) to perform the selected operation\n"
 "Type 'quit' to end the program.\n")
 calculate()
if __name__ == "__main__":
 main()

Answer 2

Starting from @theman25's answer, you could define a dictionary that maps an input to the function to use. This works, because all your functions take two arguments (i.e. you have only binary and not unary functions):

def pow_(x, y):
 d = x ** y
 return ('%d ** %d is %d' % (x, y, d))
...
func = {'+': add,
 '-': sub,
 '*': mult,
 '/': div,
 '**': pow_}
def calculate():
 while True:
 n1, n2 = user_number()
 operation = user_operation()
 if operation.lower() == 'quit':
 break
 try:
 print (func[operation](n1, n2))
 except KeyError:
 print ("That is not a valid operation!!")

Note that I renamed his sqr function to pow_, because the built-in function for this is called pow.