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Before I begin, I know there are many questions that sound a lot like this one, but my question is a little different... So here it is...

As the title may of suggested, I am trying to call a function defined in my main.py script in an imported module. However, this situation is a bit different than that of a circular import situation. I have been doing a lot with pygame recently, and decided that I was gonna make a module that contains classes for buttons, text, sounds, and so on. But I want this file to be generic so it can be used with any game or application I make. Buttons usually have draw functions and stuff like that, so I can easily pass those variables into the functions without problem. The problem comes when I get to the part where I want to check if the button is clicked, and if it is do something. I want to have it set up so that I can pass in a string argument for a command, and use the eval() command on it (python 2.7). However, it throws the error of the function not being defined. I know why this is, but I want to see if there is anything I can do to get around this issue to keep the module as "generic" as possible. Below is a basic set of code to help explain what I want to do.

module1.py

class Button(object):
    def __init__(self,x=0,y=0,image=None,command=""):
        self.x = x
        self.y = y
        self.image = image
        self.command = command

"""
Image this part filled with draw commands and stuff...
These functions work perfectly fine
"""

#Now here is the issue - local is mouse position
    def checkClick(self, local):
        #If statments here to determine if mouse over button and
        #if mouse is clicked... The part below fails
        eval(self.command)

main.py

import module1
import pygame

def quitgame():
    pygame.quit()
    quit()

local = pygame.mouse.get_pos()
b = module1.Button(command="quitgame")

#At this point lets assume that the mouse is overtop the button and the
#following function in the button will run
b.checkClick(local)

The error, as I said before states that the function I try to call is not defined. I have found a workaround for this, so I don't want answers that tell me how I can change this so it does not take a command as input. I would like however, to make it so I can input a command as an argument. Maybe I am not inputing a command the way I should, but I would like to do it like this, especially because the tkinter module allows you to enter a command as input/a variable. Maybe there is not a way to do this like I wish, but I really want to keep this code as reusable as possible with no changing required between games, and I would rather not have to put this code into my games/applications every time I make them (like I said before the code example I gave was just an example, my actual button code is much larger than what I did above). Like I said before as well, I know that there are many questions that are just like this one, but they have not helped me at all with this issue. The others suggested using scripts that are imported as well which contain addition variables and such, but I would rather not do this. Also, I have a workaround that completely gets rid of the issue, but it is not nearly as neat or easy as this would be.

As always, any help would be appreciated and thanks ahead of time for your answers in case I don't get back to you right away.

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  • Functions are first class objects in Python. You can pass them directly as parameters Commented May 13, 2016 at 2:04
  • To be honest, I am not exactly sure what the question is, but I'll post an answer. However, Alik is correct, functions are first class objects in Python. Commented May 13, 2016 at 2:11

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I want to have it set up so that I can pass in a string argument for a command, and use the eval() command on it (python 2.7).

No, no, no. Pass it a function:

# In main.py
b = module1.Button(command=quitgame)

# In module1.py
def checkClick(self, local):
    ...
    self.command()

eval is almost never the right tool for any job.

If you don't want to define a function just to pass it as a command parameter, you can use a lambda for short (single-expression) functions:

b = module1.Button(command=lambda: do_whatever(some, arguments))
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Thank you for this... I was unsure about how to do this and the first thing I was lead to was the eval() command. I can now keep all my code for this module very "generic", and I will now be able to use this for my games. Like I said before thanks for your help :).

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