Stage 3 Notes

Abstraction

You are able to use a function by reading the documentation without necessarily understanding how it works under the hood. This is abstraction.

Classes

A class is a defined set of functions and properties that are applied to each instance of the class. brad = turtle.Turtle() is calling the def __init__() function in the class Turtle. This sets aside memory that wasn't taken previously.

Classes like random, os, and turtle are a part of the Python standard library. External libraries can be imported by calling:

sudo easy_install pip
sudo pip install twilio

import twilio
print twilio.__version__

Importing Modules

Any Python source file can be used as a module by executng an import statement in some other Python source file.

import module1[, module2[,... moduleN]

Import specific attributes from a module into the current namespace using from...import

from modname import name1[, name2[, ... nameN]]

Misc Vocabulary

• Constructor - The initializing function that is caled when an instance is created. In python it is the `__init__` function.
• Instance Variable - Class property set when an object is created, and accessible by calling instance.property It is defined by `self.property` in the `__init__` function.
• Instance Method - Functions that can be called by instances and have `self` as a property. Otherwise, they are just local.

Guidelines

Google Styleguide

Class

class Class():
    def __init__(self, var1[, var2,...[]]):
        self.var1 = var1

Class Variables

Class variables have values that can be accessed by every instance of that class.

Constants should be defined with all-caps.

CLASS_VARIABLE = [1, 2, 3]

Predefined Class Attributes

• __doc__ - The class documentation string.
• __name__ - The name of the class.
• __module__ - The name of the module in which this class was defined.

Inheritance

A Child class can inherit variables and methods from a Parent class.

class Parent(object):
  def __init__(self, argP1, argP2):
    self.argP1 = argP1
    self.argP2 = argP2

class Child(Parent):
  def __init__(self, argP1, argP2, argC1):
    Parent.__init__(self, argP1, argP2)
    self.argC1 = argC1

class SuperChild(Parent):
  def __init__(self, argP1, argP2, argC1):
    super(SuperChild, self).__init__(argP1, argP2)
    self.argC1 = argC1

Using super().__init__() is a more reliable and forward compatible way of inheriting.