Python convert string to function and execute it

Question

I have several functions in the database as a strings and there is a main function that should take these functions from the database and execute them as functions, and not as text.

How I can transform a string (which describes a function) into a function with arguments and execute it in Python?

I'm tried exec but I can't return something from function and use it.

For example my function:

some_function = """
def my_random_function(some_param):
 print(some_param)
 return time.time()
"""

• Rutangaba: Hey, @Nataly Firstova, try this: stackoverflow.com/questions/7719466/…
• tandat: Function defined by exec can work like normal function, and of course you can also get the return values. Make sure you have import all the essential libraries (time in your example). PS: I will post some code for you in answer

Answer 1

100% Never do this ever under any circumstances disclaimer...

the exec statement:

code = """
def f(x):
 x = x + 1
 return x
print('This is my output.')
print(f(my_var))
"""
exec(code, {}, {"my_var": 1})

output:

This is my output.
2

• Nataly Firstova: 100% Never do this ever under any circumstances disclaimer... - why? I just want to put all functions in DB, and change it without server reload
• Keegan Cowle: It is very insecure and unreliable. See here for someone wanting to do this in PHP: stackoverflow.com/a/14653229/6014330
• Nataly Firstova: Maybe you know better way for it? I want to add end edit my functions in DB (via frontend editor) and execute it in main function on server (without redeploy)
• Keegan Cowle: That's exactly the problem. what you want to do is inherently dangerous. Its like asking to log into your bank account without a username and password. You cant do it securely.
• Keegan Cowle: The whole point of CI/CD is so that you can make changes, test them, validate it etc then promote to an environment and test again... You should not be able to change code on the fly without a deployment.

Answer 2

Function defined by exec can work like normal function, and of course you can also get the return values. Make sure you have import all the essential libraries (time in your example)

import time
some_function = """
def my_random_function(some_param):
 print(some_param)
 return time.time()
"""
exec(some_function)
return_value = my_random_function(3)
print(return_value)

output

3
1637328869.3345668

• Nataly Firstova: I got IDE error on it return_value = my_random_function(3)
• tandat: What is the error? Can you provide what the error said?
• Nataly Firstova: Unresolved reference "my_random_function"
• tandat: I guess you are using Pycharm. It is the Pycharm error since Pycharm needs to know where to find a function, and it can not find a function inside a string. Python can run it smoothly because the function will appear after the exec run.