User Classes

Classes are used to create objects that bundle data and functionality together. With this, classes are highly reusable, cleaner and more efficient. We won't hash the fundamental too hard since Python and C++ OOP are very similar. But here are some considerations:

• Python is typically 5-10x shorter than C++
• There isn't a protected, public or private keyword per-say.
• Python is better as a "glue" program or for fast implementations. Thus why we use Python in socket programming for example.

Creating an Instance in a Different File

from MyClass import MyClass

x = MyClass(name = "Iron Man")
print x.getName()

Python Specific

__init__ (Constructor)
__del__ (Deconstructor)

• It's best to name the Python file after the class name/vise-versa.
• class ClassName(object): -- to define class
• Name classes using CapWords convention
• Variables defined under classes are shared though all instances
• Variables defined in methods are only for a single instance
• When creating methods, the first parameter must be self. (similar to "this" in other languages)
• A "private" member can be created by prepending a double underscore (only prepend) to the name. It will not be visable outside of the class. __example
• Inheritance, multiple inheritance and polymorphism are all supported
• var.attrib = value is the common way to interact(dot notation)
• getattr, hasattr, setattr, delattr exist for manipulating attributes as well
• built in:

__dict__, __doc__, __name__, __module__, __bases__

• Overloadable:

__init__, __del__, __repr__, __str__, __cmp__

• dir(), type(), isinstance() are built in functions
• Once again, Python doesn't really have public, protected or private. A single prefix indicates internal usage. _ hides attributes names.

Composition vs Inheritance

• Best advice is composition over inheritance, but use inheritance when needed.
• Inheritance can complete things (especially multiple inheritance) and make larger projects confusing
• Namespace collisions are a major problem in inheritance
• Time must be given to design to effectively use inheritance, which could be time used used to stand up composition quicker.

Parent Class

Child Class

Example Call

from USResident import USResident
# pass init arguments. Must include additional argument for status
resident = USResident("Joe Smo", "citizen")
resident.setAge(23)

print "{} is a {} and is {} years of age.".format(resident.getLastName(), resident.getStatus(), resident.getAge())