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Python

Andrei Oprescu
Andrei Oprescu
9,547 Points
Posted by Andrei Oprescu
Andrei Oprescu
9,547 Points

Can you transform a string to a name of a method/function?

I am trying to create a program in python that is pretty difficult to make. I have come across a constant need to transform a string to a name of a method.

For example, I have a method called 'guessed()' and I want to call that method if a string that i get from a string is matching with that method's name. Let's say the string I use contains the string 'guessed'. Can a create a code that will call that method if it has a matching name as that string?

Thanks!

2 Answers

Alexander Davison
Alexander Davison
65,469 Points

If you must use strings—be warned though, using eval is dangerous—you can use the built-in function eval. Read the Python Docs for eval or simply call the built-in help function on eval for more information. It is unsafe to use, though, because if the user typing into the input is a clever Python programmer, he can do dangerous stuff like stopping your server or hacking your project.

If possible, do not use strings that represent the function name. You can do so in Python, as Python is also functional:

def say_hello(name):
     print("Hello {}!".format(name))

def say_bye(name):
    print("Goodbye {}!".format(name))

say_hello("Bob")  # Prints "Hello Bob!"
say_bye("Bob")  # Prints "Goodbye Bob!"

funcs = [say_hello, say_goodbye]
for func in funcs:
    func("Bob")

# Prints:
# Hello Bob!
# Goodbye Bob!

For more on functional programming in Python, watch the Treehouse course on Functional Python.

Happy coding! :zap: ~Alex

Andrei Oprescu
Andrei Oprescu
9,547 Points
Andrei Oprescu
Andrei Oprescu
9,547 Points

Hi!

I have read your comment and it was very helpful, but I have some questions on the function func:

Can it work on strings? And if yes, then how would the code look like?

Would it work on a string that is named as a method? e.g. If I have a code that would change a string called 'my_string' and output it to another string:

"self.{}".format(my_string)

Then can I use func to call that method?

If you know the answer, please reply to this comment.

Thanks!

Alexander Davison
Alexander Davison
65,469 Points

:warning: I don't recommend this: it isn't safe to use. The eval function can evaluate any expression, and that might be dangerous.

But if this is just some little thing you are building, using eval is fine.

To call a function (from self):

eval('self.{}()'.format(my_string))