Modules, Functions, Class, Metaclass, OOPs Concepts.

1. The Awesome
Modules, Functions, Class, Metaclass,
OOPs Concepts.
Part-4

2. Summary of Previous Parts
We are done with discussing the python Installation, Environment setup, Data
types in python, Basic Data structures, their syntaxes and their usage.
In the last presentation we have covered inputs, Iterators & generators, Range &
Xrange, Operators, Control flow, Branches, Expression and Order of Operation.
We will move forward with lot many things,
I hope you enjoy the show.
2

3. Modules
In python a module is something that has one or many files and has atleast
one __init__.py file.
__init__.py is usualy a blank file, but the interpreter defines a directory as a
module if the file is present inside the directory.
User has the power to override the init by allowing only those methods he/she
wants to allow.
3

4. Functions
If you know any programming language, you should probably know functions
very well. However If you don’t, function is something that has a specific set
of code for execution of some action.
It may or may not have a return statement.
In python a typical function is defined with the help of keyword ‘def’.
Syntax:
4

5. Function Example
Here is a function to print all integers less than 100.
If you call the above method just by typing print_int_lt_100() it prints all
integers less than 100.
5

6. Class
Think of a class as a blueprint. It isn't something in itself, it simply describes how to
make something. You can create lots of objects from that blueprint - known
technically as an instance.
It is a mixture of the class mechanisms found in C++ and Modula-3.
By default class members are public.
Syntax:
6

7. Metaclasses
Like i said Everything in python is an object, the class definition is also an object.
Does that mean instance of any class in python is an object of object?
Yes, It is.
A metaclass is the class of a class. Like a class defines how an instance of the class behaves, a
metaclass defines how a class behaves. A class is an instance of a metaclass.
7

8. Object Oriented
Python In OOP programmers define not only
the datatype of a data structure,
but also the types of operations
(functions) that can be applied to
the data structure.
8
Oops Concepts like inheritance,
polymorphism etc.

9. Terms
class variable
data member
self
__init__
__del__
static method
class method
inheritance 9

10. Class Members, self, constructors and destructors
Forget about class members, data members
etc and think about an UNIT.
This UNIT has it’s attributes, methods and
what not.
A perfect example for class in real time is an
UNIT in an organisation.
Or a real time Person Class.
Person can have age, name etc and the
person can take various actions.
Then there is something called self.
There needs to be something that connects
within the unit that validates the data
member and methods.
There needs to be something or some power
that creates the instance and assigns
values.
There needs to be something that destroys
the instance.
10

11. Old Style vs New Style Python Classes
Old Style classes does not inherit from any
other class.
Old style classes are not there anymore in
python 3.x
Old style classes are good.
1. New style classes inherits from object or
other new style classes.
2. New style classes are The Thing now with
many new features, changed MRO
standards and many more.
3. New style classes are better.
11

12. ThanksStay Tuned for the next part. Enjoy !!
12