exec() not working when trying to execute a string containing the command "abs.__doc_

I am trying to execute the command abs.__ doc__ inside the exec() function but for some reason it does not work.

function = input("Please enter the name of a function: ")
proper_string = str(function)   "."   "__doc__"
exec(proper_string)

Essentially, I am going through a series of exercises and one of them asks to provide a short description of the entered function using the __ doc__ attribute. I am trying with abs.__ doc__ but my command line comes empty. When I run python in the command line and type in abs.__ doc__ without anything else it works, but for some reason when I try to input it as a string into the exec() command I can't get any output. Any help would be greatly appreciated. (I have deliberately added spaces in this description concerning the attribute I am trying to use because I get bold type without any of the underscores showing.)

As a note, I do not think I have imported any libraries that could interfere, but these are the libraries that I have imported so far:

import sys
import datetime
from math import pi

My Python version is Python 3.10.4. My operating system is Windows 10.

CodePudding user response：

abs.__doc__ is a string. You should use eval instead of exec to get the string.

Example:

function = input("Please enter the name of a function: ")
proper_string = str(function)   "."   "__doc__"
doc = eval(proper_string)

CodePudding user response：

You can access it using globals():

def func():
  """Func"""
  pass

mine = input("Please enter the name of a function: ")
print(globals()[mine].__doc__)

globals() return a dictionary that keeps track of all the module-level definitions. globals()[mine] is just trying to lookup for the name stored in mine; which is a function object if you assign mine to "func".

As for abs and int -- since these are builtins -- you can look it up directly using getattr(abs, "__doc__") or a more explicit: getattr(__builtins__, "abs").__doc__.

There are different ways to lookup for a python object corresponding to a given string; it's better not to use exec and eval unless really needed.