The init Constructor: Why Every Method Starts With self

How can a method name an object that doesn't exist yet — and why does `self.x = xval` outlive the plain `x = xval` beside it?

Finger exercises

Short drills on what this video just taught. Write the code, run the checks, and reveal the answer only if you are stuck.

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Exercise 1 of 5

Write the constructor

The class header for Coordinate is already written, its body still holding nothing but a docstring. Add the constructor to that body. Keep the parameter names xval and yval, and store the two values on the object as attributes named x and y.

The class itself is this exercise's answer — there is no separate variable to assign.

# Exercise 1: give Coordinate a constructor that stores an x and a y on the object.
class Coordinate(object):
    """ A coordinate made up of an x and y value """
    # your code here

# Exercise 1: give Coordinate a constructor that stores an x and a y on the object.
class Coordinate(object):
    """ A coordinate made up of an x and y value """
    # your code here

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the class defines a constructor of its own

the constructor takes self plus the parameters xval and yval

a new coordinate carries the two values as the attributes x and y

every coordinate carries its own x and y

←Previous class Coordinate(object): Implementing a Type vs Using It Next Creating Instances: Coordinate(3, 4), Dot Notation, and Memory →

The __init__ Constructor: Why Every Method Starts With self

Write the constructor

The __init__ Constructor: Why Every Method Starts With self

Write the constructor

The init Constructor: Why Every Method Starts With self

The init Constructor: Why Every Method Starts With self