#python

Value equality vs identity

• Value –> equivalent contents
• Identity –> same object

Binding Names to Objects

p = [1,2,3]
q = [1,2,3] 
p == q  # --> True    --> val is same
p is q  # --> False   --> not same obj

a = "first"
b = "first"
a is b # --> True

• NOTE:
  • Immutable object (str, int tuple) refers to same obj if values are same
  • Mutable obj always create new object

Pass by object reference

• Python uses neither Pass by Value nor Pass by Reference
• But it uses Pass by Object Reference

First Class functions in Python

• In Python when functions treated like any other variable then they are term as First-class functions
• Properties of first class functions:

  • Assign to a variable.
  • Pass the function as a parameter to another function.
  • Return a function from another function.

Nested function

• Function defined inside another function –> nested function
• Nested functions are able to access variables of the enclosing scope.

def print_msg(msg):
  def printer():
    print(msg)
  printer()

print_msg("Hello")
# Output: Hello

Python Decorators

• It’s a very powerful and useful tool in Python
• It allows to add functionality to an existing function or class.

7. Multi-threading

Multithreading allows you to break down an application into multiple sub-tasks and run these tasks simultaneously.

If you use multithreading properly, your application speed, performance, and rendering can all be improved.

Multithreading is defined as the ability of a processor to execute multiple threads concurrently.

Multi Processing

Multiprocessing refers to the ability of a system to support more than one processor at the same time.

Applications in a multiprocessing system are broken to smaller routines that run independently. The operating system allocates these threads to the processors improving performance of the system.

1. OOPs, Concept

• Object Oriented Programming
• OOP is a specific way of designing a program by using classes and objects
• It allows us to relate program with real-world objects, like properties and behaviors
• Properties
  • It defines the state of the object.
  • Like: name, age, address etc. that store data of the object
• Behaviors
  • Are the actions our object can take.
  • Like: talking, breathing, running etc
  • Oftentimes, this involves using or modifying the properties of our object.

2. Variables/Attribute

In a class all the variables are term as Attribute

There are 3 types of variables are allowed.

1. Instance/Regular Variables - - Object Level Variables
2. Class/Static Variables - - Class Level Variables
3. Local variables - - Method Level Variables

• Attributes are looked first in the instance and then in the class

3. Methods in python

• Function
  • Function is block of code that is also called by its name(independent)
  • Function does not deal with Class and its instance concept.
• Methods
  • Method is called by its name, but it is associated to an object (dependent)

The following are various types of allowed methods:

1. Instance Methods - - self
2. Class Methods - - cls
3. Static Methods

Type Checking/Annotations in Python

• Type Annotations are a new feature added in PEP 484 that allow for adding type hints to variables.
• They are used to inform someone reading the code what the type of a variable should be.
• This brings a sense of statically typed control to the dynamically typed Python
• Usage

  • Annotate Argument
  • Annotate Return type
  • Annotate Variable