Calling Functions Within Classes: A Practical Approach

In object-oriented programming, classes encapsulate data and functionality, organizing them into logical entities. When you need to perform operations on these objects, you can define member functions within the class. However, it's not always clear how to call one function from within another when both are defined in the same class.

The Issue:

Consider the following code that calculates distances between coordinates:

class Coordinates:
    def distToPoint(self, p):
        # Calculate distance using Pythagoras' theorem

    def isNear(self, p):
        # How do we call distToPoint from isNear?

In this example, we want to determine if a point is near another point using the distToPoint function. How do we invoke this function within the isNear function?

The Solution:

To call a member function within the same class, we need to use the instance of the class (referred to as self by convention) to access its methods. The corrected isNear function would look like this:

class Coordinates:
    def distToPoint(self, p):
        # Calculate distance using Pythagoras' theorem

    def isNear(self, p):
        self.distToPoint(p)
        # Continue with other operations

By adding self before distToPoint, we are explicitly indicating that we want to call the member function distToPoint on the instance self of the Coordinates class.

Example Usage:

To use this code, you would create an instance of the Coordinates class and then call the isNear function on that instance:

coordinates = Coordinates()
coordinates.isNear(another_point)

This will calculate the distance between the instance's coordinates and the specified another_point using the distToPoint function.