# Multiple numbers calculator

This is my first ever Python program so I would really like to know if it's any good (I mean if it is well writen), and if not then how to make it better. I would also like to know if there is a way to get all the veriables in one line without a space between them.

This calculator is basicly this calculator which I wrote in C++ upgraded and writen in Python.

def calculate(num1, num2, act):
if(act=='+'):
total=num1+num2
elif(act=='-'):
total=num1-num2
elif(act=='*'):
total=num1*num2
elif(act=='/'):
total=num1/num2
else:
print("input not recognized")

def calc2():
user_input=input("Enter a num1 act num2 (with a space between them): ")   #Gets the values
var1, action, var2=user_input.split()     #assigns the values into the variables
if(action=='/' and var2==0):      #checks for division by 0
print("YOU CAN'T DIVIDE BY ZERO!!!")
else:
print(calculate(float(var1), float(var2), action))     #calls the 'calculating' function, recives and prints the total of act

def calc3():
user_input=input("Enter a num1 act1 num2 act2 num3 (with a space between them): ")      #Gets the values
var1, action1, var2, action2, var3=user_input.split()           #assigns the values into the variables
if(action1=='/' and var2==0 or action2=='/' and var3==0):      #checks for division by 0
print("YOU CAN'T DIVIDE BY ZERO!!!")
elif((action2=='*' or action2=='/') and (action1=='+' or action2=='-')):    #checks if act2 should be done before act1 (order of operation)
total=calculate(float(var2), float(var3), action2)     #calls the 'calculating' function, recives the total of act2
print(calculate(float(var1), float(total), action1))     #calls the 'calculating' function, assigns the total of act2 as num2, recives and prints the total of act1
else:                                                             #act1 is done before act2 (order of operation)
total=calculate(float(var1), float(var2), action1)         #calls the 'calculating' function, recives the total of act1
print(calculate(float(total), float(var3), action2))     #calls the 'calculating' function, assigns the total of act1 as num1, recives and prints the total of act2

def main():
amount=float(input("How many numbers? (2-3 numbers) "))
if(amount==2):
calc2()
elif(amount==3):
calc3()
else:
print("I SAID TWO OR THREE NUMBERS")

main()           #starts program


## Input/Output

Input:2 + 3 * 4
Output:14

There are some places where you can dictionaries instead of if/elif/else statements, I will analyze one here:

if(act=='+'):
total=num1+num2
elif(act=='-'):
total=num1-num2
elif(act=='*'):
total=num1*num2
elif(act=='/'):
total=num1/num2
else:
print("input not recognized")


Is often re-written as a dictionary. So, you could create a dictionary called OPS and write:

import operator

OPS = {
'-' : operator.sub,
...
}
ERROR = lambda arg1, arg2: print("input not recognized")


You can then you can do:

def calculate(num1, num2, act):
return OPS.get(act, ERROR)(num1, num2)


This tries getting the particular key which is a function. It then calls it. If the operator is not found, it defaults to the ERROR.

• I would use a try..except KeyError instead of dict.get, but otherwise nice answer. – Graipher Dec 17 '16 at 7:16