How to dynamically call different functions based on user input

Question

I am looking to figure out how I can dynamically call certain functions based on user input. For example, I have the following code that just does simple math based on a series of keyword arguments.

def calculate(**kwargs):
    operation = kwargs.get("operation")

    def add(num1,num2,msg="The result is"):
          return f"{msg} {float(num1 + num2)}" if kwargs.get("make_float") else f"{msg} {float(num1 + num2)}"

    def sub(num1,num2,msg="The result is"):
          return f"{msg} {float(num1 - num2)}" if kwargs.get("make_float") else f"{msg} {num1 - num2}"

    def multiply(num1,num2,msg="The result is"):
          return f"{msg} {float(num1 * num2)}" if kwargs.get("make_float") else f"{msg} {(num1 * num2)}"

    def divide(num1,num2,msg="The result is"):
          return f"{msg} {float(num1 / num2)}" if kwargs.get("make_float") else f"{msg} {(num1 / num2)}"

    return operation(kwargs.get("first"),kwargs.get("second"),kwargs.get("message"))

print(calculate(make_float=False, operation='add', message='You just added', first=2, second=4))

I know there are better ways to do a calculator of course, but the point here is I want to try and avoid using a bunch of if/elses to check and see what function to run between add/sub/divide/multiply. I thought I could save it into a variable called "operation" and use that to call the proper function, but that will not work as a string isn't callable.

Essentially I want to be able to dynamically call a function based on user input (assuming the user input is exactly the name of the function) but I am unsure how.

Mark Ransom · Accepted Answer · 2021-07-11 02:40:46Z

2

Since functions are objects in Python, it's easy to make a dictionary pairing keywords with functions.

action_dict = {'add': add,
               'sub': sub,
               # ...
              }

if operation in action_dict:
    action_dict[operation](num1, num2)

answered Jul 11, 2021 at 2:40

Mark Ransom

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1 Comment

ACanadianEh Over a year ago

Right that makes sense. Thanks for the help

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