How can I call a function inside a class?

Question

I have a class in globals.py as:

#!/usr/bin/env python

class fg():                                                                                                                           
    def red(text):     return f'\033[00;49;031m{text}\033[0m'
    def heading(text): return red(text)

and I have the testrun.py script as:

#!/usr/bin/env python

from globals import fg

# Command 1:
print(fg.red("My text"))
# prints as expected


# Command 2:
print(fg.heading("My text"))
# throws the error: NameError: name 'red' is not defined

The question is how can call red function within the heading function.

Answer 1

When calling member functions you have to use the self argument, and initiate the class. So the calls would be like this.

class fg():                                                                                                                           
    def red(self, text):
        return f'\033[00;49;031m{text}\033[0m'
    def heading(self, text):
        return self.red(text)

and then

print(fg().red("My text"))
# prints as expected


# Command 2:
print(fg().heading("My text"))

Answer 2

First, there is a typo in your code. You misspelled return as "retrun". Also, you can't call a class method directly. Here is what you're probably looking for.

class fg():
    def __init__(self, text):
        self.text = text
    
    def red(self):
        return f'\033[00;49;031m{self.text}\033[0m'

    def heading(self):
        return self.red()

And now you can import the file.

from globals import fg

obj = fg("My text")
print(obj.red())
print(obj.heading())

I have made a lot of modifications to your code.

1. Use self to call the class methods
2. If the text parameter is the same for both, you need not pass it every time you call these methods. Instead, you can initialize that in the self method itself.
3. You first need to create an object of a class to access its methods (called constructors).