All functions are executing but I only called one in python-CodePudding

The program is executing all the functions and I only want it to execute the one that is called in the function_call[operation] dictionary key.

   # Define functions for addition, subtraction, division, and multiplication
 # Write the equation and its output to a file 
    def add(num1, num2):
      answer =  num1   num2
       with open("equation.txt", "w") as equation:
         return equation.write(f" {num1}   {num2} = {answer}")
    
     def subtract(num1, num2):
         answer =  num1 - num2
           with open("equation.txt", "w") as equation:
             return equation.write(f" {num1} - {num2} = {answer}")
    
     def multiply(num1, num2): 
        answer =  num1 * num2
          with open("equation.txt", "w") as equation:
            return equation.write(f" {num1} * {num2} = {answer}")
    
     def divide(num1, num2):
        answer =  num1/num2 
          with open("equation.txt", "w") as equation:
            return  equation.write(f" {num1} / {num2} = {answer}")
    
    # input first number
    # input operation
    # input second number 
       
      num1 = int(input("Please enter a valid first number: "))

      operation = input('''   Choose between:
         : addition operation
       - : subtract operation
       * : multiply operation
       / : divide operation                
       :  ''') 

       num2 = int(input("Please enter a valid second number: "))

   # create dictionary with operation input as key and corresponding value as function
   # call diction value with operation variable as key to call the desired function or operation to be executed 
      function_call = {
         " " : add(num1, num2),
         "-" : subtract(num1, num2),
         "*" : multiply(num1, num2),
         "/" : divide(num1, num2),
    
       }

       print(function_call[operation])

CodePudding user response：

func = function_call[operation]
print(func(num1, num2))

Functions in Python are objects. So you could handle them as objects and interoperate between other objects. All you need is just provide arguments to run it (call)

CodePudding user response：

The problem is that when you define the function_call dictionary, you're calling all of the functions and storing the results of those calls in the dictionary:

      function_call = {
         " " : add(num1, num2),
         "-" : subtract(num1, num2),
         "*" : multiply(num1, num2),
         "/" : divide(num1, num2),
       }

Instead, put the functions themselves in the dictionary without calling them yet:

      function_call = {
         " " : add,
         "-" : subtract,
         "*" : multiply,
         "/" : divide,
       }

and then call the appropriate function after you fetch it from the dictionary:

print(function_call[operation](num1, num2))

CodePudding user response：

function_call = {
     " " : add(num1, num2),
     "-" : subtract(num1, num2),
     "*" : multiply(num1, num2),
     "/" : divide(num1, num2),    
 }

Because there are parentheses after the function names, they are called during the definition of the dictionary.

If you don't want that, then don't put the parentheses:

function_call = {
     " " : add,
     "-" : subtract,
     "*" : multiply,
     "/" : divide,
 }