Python_Learning

Installation of Python in your System

go to website- www.python.org
click on dowloads select you OS accordingly.
Download the latest version.
Open download file and follow the steps

Install VSCode

go to website- www.code.visualstudio.com
click on dowloads select you OS accordingly.
Download the latest version.
Open download file and follow the steps

Open window.powershell

python in powershell. then you will enter in python world.
exit() write in powershell you will come out from python.
for just check version of Python you installed just type python --version in powershell.
pip for just create python environment like- install,uninstall Packages. etc.
pip --version for check version and where our "pip" is installed.

What is pyhton?

Python is programing language which help us to communicate with computer or laptop even with any type of opreating system. It is very simple and easy to understand like reading a simple "English". Python pseudo code nature make python easy to learn for non-codder to just start learning coding and machine learning

What is PIP?

Pip is the package maneger for pyhton like Node or npm in package manager for javascript/Node.js.you can use pip to install packages or a module on your system.

what are Modules?

Module is a file with code written by somebody else which you can import byt installing that module in you program using pip

Types of Modules?

*** Built-in => which you during installation of python in your system.*** *** External => which you have to install using "pip" in your system.***

Simple example of Python working that is you can use pyhton as "Calculater" REPl - Read Evaluate Print loop

Comments?

Basiclly developer use this for give instruction in code base. Comments will never show on Browser when we run file on web-browser. Comment can be single line or Multiple line

Key-Features of Python

Easy to understand = Fast Development
Free and open source
Work with every Opreating system.
Enjoy workin with it.

World best code we gonna written

for Javascript we use console.log("Hello World") ==> print("Hello World") for Python Language

for "run" pyhton we need just click on Run button.
External command for terminal python {file.name} you can use shortcut just write "pyhton" space you file names first letter -> "python h" then press tab it will auto-complete name and after getting name hit "Enter" button.

Install Python Extension

Open visual studion code.
Click on "Extension" tab.
Search "Python" in search-bar.
Click on Install button.
Congratulation! You done it.
Final and last step select pyhton Interprater.

Variables and Datatypes in Python

Variable is name given to value for storing in your program or with Declare a varible name with value you can use that anywher in that particuler file TO declare a variable name you have to follow set of Rules:

variable name can contain alphabet,numbers,underscore.
variable name can never be start with number.
variable name can only start with Alphabet.
you can't give space inside variable name.

Datatype in python- mostly used datatype are as following:- Integerns Floating point numbers Strings Boolean None

Operators in Pyhton

1. Arithmetic operators => "+,-,/,*" common examples.
2. Assignment operators => "=,+=,-=" you will use in further steps.
3. Comperison operators => "==,>,>=,<,<=,!=" for compare value and type also.
4. Logical operators => "and,or,not" check logic in functions.

type() functions and typecasting

if you have number in string and you want to add number in that string, Just put variable name as parameter in int(varibele.name) then string number will be convert in number or integer. But it is valid on number or integers.

String

String is just a Datatype in Python You can write with three ways

Single quoted string -> course="Pyhton"
Double quoted string -> language="Hindi"
Triple quoted string -> easy='''Yes'''

String Slicing

slice means chop into peaces "Simple words to make every single words as string you can use "Slicing" in pyhton.

what you need to know for use slicing?

Index -> this is given by pyhton internaly to string characters.
Length -> total words or characters in string is Length of that string.
Example string="Varinder" print(name[0]) will print only first letter "V" of string.
print(name[0:4]) will print "Vari" ii will print index-number=[0,1,2,3] not print 4 number because index=length-1.

Can you use Negtive index number in Python?

Answer is YES!. Mostly case where you can use this is when you have to print last Index of string but you don't know the length of string.

Example= "print last index of this string" --> you don't know the length then how print last[index]?
Simple -> print(Example[-1])

Can you skip the index number in Python?

Answer is Yes. How! you are thinking about it...let understand with following example:

Example= "Varinder" --> skip "ar" and "nd"
simple print(Example[0:7:3]) --> you will get "Vie".

String functions in Python?

Find length of string using len(). "len" is nothing just short form of length. syntax to write len function print(len(name_of_string))
To check string endwiths given entry or not (it will return true || false).
syntax to use endswith function print(string..endwith(given_value))
To count how words are present in string equal to given letter(value).
syntax to write count function print(variable_name.count(value_for_count))
To make first letter capital in string starting use Capital() function syntax to write Capital() function print(variable_name.capitalize()))
To Find word is present in string equal to given letter(value).
syntax to write find() function print(variable_name.find(value_for_count))
it will provide first word index if more then 1 same words are present in string
To Replace word is present in string equal to given letter(value).
syntax to write replace() function print(variable_name.replace(value_want_replace,value_want_after_replace))
it will replace all words if more then 1 same words are present in string with new value

Escape sequences characters

Characters after "" will come know as Escape sequence character Example- \n,\t,',\ etc

Lists and tuples in Python

-- List are basically set of values of any type. Any type menas it can be Strings, Boolean, Integers, Floating points etc.
Booleans list - [true,false,true] Integers list - [1,2,3,45,6,8] Strings list - ["Phython","Java","C#","Javascript"] Floating points list - [0.35,1.52,35.89,1.105]

List Indexing -- Index is always same in every case: - it will start from number "0". - It will stop at length-1 index number.

Can change value of list -- Answer is Yes! - a=[1,2,4,3] --> for change value you index of that place where you want to change - a[2]=3 --> now "4" will change with "3" - a[3]=4 --> now "3" will change with "4"

Can string Functions can implemen in Lists? -- Answer is Yes! but not all of them - Len() to find length of list. - Slicing also can be implement in list like "[0:4]"

List Methods

For more understand through examples check file "ListMethods.py" -- .Sort(): for sorting of list in assending order. -- .reverse(): for sorting of list in desending order. -- .append(): for add someting in the end of list. -- .insert(): for add something on selected index value. -- .pop(): to delete value from list by index number or if not give any index number then last item will be deleted. -- .remove() to remove item by Value providing it. for more methods

Link for Method List

Tuples

Immutable in nature->menas you can't make changes in it -- Tuples are used to store multiple items in a single variable. Tuple is one of 4 built-in data types in Python used to store collections of data, the other 3 are List, Set, and Dictionary, all with different qualities and usage. A tuple is a collection which is ordered and unchangeable. - Tuple types:

t=() --> Empty tuple.
t=(1,) --> Tuple with Single element Comma is must to declare tuple with single item

Can you chnage values in tuple like you don in "List"

 -- No,you got an error because you read values from tuple but cannot chnage that value.

for more see practical check file "Tuples.py" code

Tuple Method

-- To count how many time same word in tuple comes. syntax for this function count() - print(tuple.name(value_for_check)) -- To first occurence of value in tuple. syntax for this function count() - print(tuple.index(value_for_check))

Link for Tupple More Information

Dictoinery and Sets in python

Dictionary mean not Oxford dictionary

-- In simple mean you work with Javascript than you Know about "Objects". Object have "Key-value" pairs. Same in Python this known as "Dictionary".

More simplfy it than you can say "Key" is like when you search on google you write somthing in "input tag" that is key and anwser you get from in revert that is called "Value".

syntax

Examples:

dictionary={ "name":"Varinder", "age":27, "developer":True, "project":[1,2,3,4,5] } #name=key #Varinder=value Data-Types you can put in Dictionary
Interger("int")
Boolen ("bol")
String-Literal("str")
List("lst")
Dictionary("dic")

Properties of Python Dictionaries:

Unordered in manner
Mutable(you can change then according your need)
Indexed
Duplicasy is not allowed

Distionary Methods:

For print all key in list manner: print(Dictionary.name.keys()) this will all key of your "Dictionary"
1. can check type of keys? - Yes! very simple to check write code as show here "print(type(Dictionary.name.keys()))
  - type= "dict_keys"
2. can you print keys in list manner? - Yes! very simple to check write code as show here "print(list(Dictionary.name.keys()))
For print all Values in list manner: print(Dictionary.name.value()) this will all Value of your "Dictionary"
1. can check type of keys?
- Yes! very simple to check write code as show here "print(type(Dictionary.name.values()))
- type= "dict_values"
1. can you print values in list manner? - Yes! very simple to check write code as show here "print(list(Dictionary.name.values()))
  - For get in return list of (key,value) tuples print(Disctionary.name.items())

- For update new key-value pair in dictionary
newItem={
    "Mac-Book":"New_wish"
}            
*Dictionary.name(newitem)*
*print(Dictionary.name(name_of_item))*

- For get value of key you can use ".get()" 
*print(Dicationary.name.get("key_name"))*
 but you may confuse here that you can value by simply write
 *print(Dictionary.name["key_name"])* then what is nee of ".get()" ?
 simple reason behind this if you don't have that "value" then ".get()" will show "NONE" where simple "["key_name"] will through error because in simple ["key_value"] you have take care that key-name should be there which you written there.


 <a href="https://docs.python.org/3/tutorial/datastructures.html#dictionaries">More Dictionary Methods</a>

Set in Python

Set is a Collection of non-repetitve elements

for example check first example in "Set.py" file. For more simply this You can say that "Sets" are data-types which contain only unique elements means value should be diffrent from each other

Properties of Python Sets:

Unordered in manner
Immutable(you can't change then according your need)
Sets are unindexed(you can get them by index number)
Duplicasy is not allowed means you can't write same value more than one time.

Sets Methods

".Add()" to add element or value in sets Set.name.add(value_or_elements) is syntax to use method
-- You can't same element two or more time -- -- You can't add list or dictionary in Sets -- -- You can only add Immutable data-type like: "tuples" --
"Len()" to print length of Sets print(len(Set.name)) is syntax to use methods
".Remove()" from remove element from Sets Set.name.remove(value_to_remove) os syntax to use method
".pop()" remove element from set and return that element print(Set.name.pop()) is systax to use mehtod
".clear()" from clean that set or remove everything from Set Set.name.clear() is syntax to use method
".Union() to get all elements present in both sets is Syntax to use method
".Intersection() to get "Same" elements present in both sets is Syntax to use method

Conditoional Experssion in Python

-- Conditional experssions means when have some situation or condition to full fill "If" or "else" best example of this is you can read below: when are in school in 10th standard you for "Iphone" to your "Dad" and he say if you "marks" is greater then 90% than you will get it or if you score are above 80% than you will get "Samsung". If your marks above 70% than "realme" or if you get below than 60% than "Chappal" this is called Conditional Expression

Syntax

if(condition): print("yes")
else : print("no") one more syntax you that elif which means (else if). this is used when conditions are more then two
elif(condition): print("Maybe")

Relational operators

we already dicussed this here is some examples of relational operators: "==",">=","<=" etc.

Logical operators

logical operators operate on conditional statement example: "and", "or","not"

"and" if both conditions are true than it go inside if statement.
"or" if from both condition one will be true than it will go inside the statement
"not" is use to make true into false and false into true.

IS or IN uses

you mostly gonna use if,elif or else but you should know about this things also what "Is" work for? what "In" work for?

Loops in Python

if you want print "Hello world" 1000 times than you will shock and start thinking like i have write code "print("hello world")" 1000 times. You answer is like "bhai mujhe nai sikhni yeh "coding-voding" main chla ghr bye!"

what is your reaction when i tell you that it can be done in two lines of code!!!

-- Yes Loops gonna help us in this work --

Types of loops in Python

while loop
for loop

While loop -

- Syntax of while loop is show  below:  

While condition :  #loop will until it == true#
        #here we right body code of loop

For loop -

- Syntax of while loop is show  below:

for ("name of initial value") in varibale or etc.
     for "total" in "table" :
                print(total)

Range Function in Python

if you wanna print sequences of numbers than this will help you how? you wanna se than come to file name "Loops.py line no.46" means you can set range from where to till you want to print Question will come in your mind: 1. Can we choose any starting point according to our choice? ans. Yes, you can do this. 2. Can we stop where we want to stop printing of numbers? ans. Yes, with providing upto value. 3. Can we skip number according to odd/even format? ans. Yes, you can do this. 4. How can we do this? Ans.For clearification come in file name "RangeFunctions.py".

Else conditon with For loop -

- this will help to now that our condition change to False. "you can asume this" example in "RangeFunction.py" file.

Break statement in Pyhton -

- Break is used to stop the loop on certain point or conditon. when that point is valid or condition gonna true loop will stop automaticaly. Let understand with example in file name "RangeFunctions.py".

Continue statement in Pyhton -

- Continue will use to skip something from intration on problem .More easy way "jab hume kisi ko ignore krna ho to bus uski baat  unsunna krdo." Same we are doing this here Let understand with example in file name "RangeFunctions.py".

Pass statement in Pyhton -

- We mostly use "Pass" on there where if condition is pass but nothing to do with that in those cases you can use Pass.
  *Example hume logo ko jab koi kam nai krne mood nai hota to hum kisi ki baat ka koi rply nai dete*
  I know you need example on this and i know you where you have to check.

Functions in Pyhton -

- A function is set of statement to do specific task

for large scale working where can't track of working of program on that place functions played very good role. Functions are reuseable in nature

Syntax for Functions

"def" id used for telling that this is function.
Now how we can declare a function

def Function_name(value): return (logic) print(value).

Type of Funtions in pyhton -

Basically two types of function are in pyhton:

Built in function you get this when you install pyhton in you system
User defined function which you make according to your work

Example of In-Built functions
1. print() --> to print our result
2. sum() --> to sum our integers
3. range() --> to decide range of print(result)
4. len() --> to check length of value ... to check more in-built function click below link: In-Built Functions
Example of In-Built functions find pecent of students scores:
```
  def percent(score):
   return (sum(score)/600*100)
   percent=percent(score)result with this function.
   print(percent) 
```
- Function Arguments: you can pass value in function as "argument" and function will return a value to print in your terminal as shown in upper example.
- Default argument: this will help you in two ways:
  1. you make function where user have to put input but he/she just simple print than they got a default value which you set while making funtions.
  2. You can use this just simple check that functions is working or not.
  Example
```
name=input("Enter Name \n")
def sayHi(name="Viewers):
print("Hello good morning " + name)
sayHi(name)```
```

Recursion in pyhton

when function call itself that is called "Recursion". More simple way you provide a task to Function than it will processing till answer will not come.

Let understand will factorial Example

 fact=5
 factorial=1
 for i in range(fact):
   factorial=factorial*(i+1)
 print(factorial)

Now same work with Functions

  n=int(input('Enter number \n'))
  def Factorial(n):
      start=1
      for i in range(n):
          start=start*(i+1)
      return start
  print(f"Factorial of {n} in {Factorial(n)}")         
  print(Factorial(n))

Recursive manner with Function but you hav to give base case when function comes to base-case than it will stop and return a value for that case Example

 def Recursive_Factorial(n):
      if n==1 or n==0:
          return 1
      return n*Recursive_Factorial(n-1)     
  print(f"Factorial of {n} in {Recursive_Factorial(n)}  ")

Strip() function used for remove space from start and at end of value

Another useFull topic of function -

for print Random for given range use:

   randon.randint(start_range, end_range)

File I/O(Input/Output) in Python -

Let understand with basic example like you are chating with your "GF" you want to send a "Heart Imogi" if you already send it before you simply copy that and paste it again but what happen if "Heart Imogi" is not in your phone than you tried to install external package of "Imogies" that which create new File of "imogies" for your use.

Now with Book Defination "Using input() and print() Function. A good program should effectively communicate any input in Python from the user and display a result to the outside world. A user can give a program input manually from a keyboard or use data from an external source, such as a file or a database."

Typee of Files
- There are two types of files:
1. Text Files (.txt etc)
2. Binary Files (.jpg, .dat etc)
Python has lot of functions for reading, writing, updating and deleting files.
Opening a File
- Python has "open()" function for opening file.this is built in function.
Modes to open files
1. r --> for read file
2. w --> to write file
3. - --> to update file
4. a --> to appending file
5. rb --> to open file in binary mode
6. rt --> to opne file in text mode
Read file in python-
1. for use this you have to pass two parameters Filename or mode
```
   open("file_name","command")
```
command can be - read, write, update and delete
1. Functions to "read" a file
  1. ".read()" to read all content.
```
  data=open("file_name","r")
  info=data.read()
  print(info)
  data.close()
```
  or
```
data=open("file_name")
info=data.read()
print(info)
data.close()
```
  1. ".read(value)" value for how much words you want to read
```
data=open("file_name")
info=data.read(5)
print(info)
data.close()
```
  1. ".readline()" function will print every time one new line
```
   file=open("myInfo.txt")
   letRead=file.readline()
   print(letRead)
   file.close()
```
Write file in python -
1. for use this use this function syntax is:
```
  letFile= open("mydata.txt",'w') 
  Details= letFile.write("Make this file with name mydata")
  letFile.close()
```
2. to append data in this file: "a" use as append command
```
    letFile= open("mydata.txt",'a') 
    Details= letFile.write("Make this file with name mydata")
    letFile.close()
```
Context for auto-close

You can both thing read and write with this syntax 1. to read file with this syntax: with open('mydata.txt','r') as f: a=f.read() print(a) 2. to write file with this syntax: with open('mydata.txt','a') as f: a=f.write() print(a)

Object oriented programing (OOPs)

solving s problem using object or creating a object is called object oriented programing.for reusing of code is more focuesd in this concept. that is called "DRY principle".DRY --> Don't repeat yourself.

Class

 - Class is nothing judt blueprint of objects.

they never take memory untill you don't usethis

Classname which is wrtiten in PascalCase manner -->first letter is capital in PascelCase.
```
Class Students:
         #methods & variables
```

Object

 - object is an instantation of class. after object instatation memory will be allocated to class.where user don't need to borther that how this will work.

why we use OOPs or what need of this?

If your website go bigger day by day than difficult to handle or make a change in code because if lines of code is more than 1000 than you have find you form code than you say with help of "ctrl+f" but actual this not gonna help you but Object Oriented Programing(OOPs) will help you through this process. when you declare a class than you can tell that this class for particuler work.

Modelling a problem in OOPs?

Identfiy problem in following manner:
1. Nown --> Class_name
2. Adjective --> Attributes
3. Verbs --> Methods

Class Attributes

An attribute that belongs to the class rather than a particular object Example :

  class Employee:
       company="Google"     --> [specific to each class]

   varinder=Employee()      --> [Object instantiation]
   varinder.campany
   Employee.company="Youtube" ->[Changin class attribute]

Instance Attributes

An attribute that belongs to the instance (object).More simplyfiy this than you can say uniques things for different object: Example from previous class:
```
  varinder.name="Varinder Brar"
  varinder.salary="75k"      --> [Adding instance attribute]
```
Note: Instance attributes take preference over class attributes during assognment & retrival it will check varinder is present in object?

Self parameter

 self refers to the instance of the class. It is automatically passed with a function call from an object

 ```
    varinder.getSalary()  --> here self varidner
                    |_______ equiratent to employee.getSalary(varinder)  
 ```

 *this function get salary is defined as:*

 ```
    class Employee:
          company="Google"
          def getSalary(self):
                    print("salary is not there)
 ```                                           

# Statix methods
  like if you need a function where you don't want use self parameter on that place you can use static method.

  ```
     @staticmethod    --->decorater to mark greet as a static method
        def greet():
            print("Hello Bhai")
  ```

# "__init__()" Constructor
   this is a special method which is first run as soon as the object is created. this also known as constructor.
   *It takes self argument and can also take futher arguments*

   ```
      class Data:
    info="names"
    def __init__(self,name,company,role,valueofcampany):
    self.name=name
    self.company=company
    self.role=role
    self.valueofcompany=valueofcampany
    print("Name list is ready")

    def details(self):
    print(f"The name is {self.name}")
    print(f"The company name is {self.company}")        
    print(f"Role in campany as a {self.role}")        
    print(f"The value of campany is {self.valueofcompany}")        


    Brar=Data("Varinder Brar","Youngstr","Owner",1000)              
    ```

Inheritance

Inheritance is way to create new class from existing class or already working class. we divided this into two parts:

Base Class
Drive class Explaination:

Base Class:

 - In Simple words you can say that class we make first or parent class of children classses.
 ***Syntax***

  class Emplyoee:
       company="JavascriptFolks"
   
       def showDetails(self):
     print("Emplyoee Data")

Drive Class:

 - this class have attributes or parts are you take from parent class mean Base class and other custom things you can addon accordinh to your need.
 ***Syntax***
 ```
    class Programers(Emplyoee):
               language="Python"
               def getlanguage(self):
    print(f"this language is {self.language}")
 ```

You can over-riding drive class

Type of Inheritance:

Single Inheritance
Multiple Inheritance
Multi-level Inheritnace

Explaination:

**Single Inheritance**:
- Single inheritance called in that situation when child or drive class inherite only from single parent or base class.

**Multiple Inheritance**
- Multiple inheritance occurs when the child or drive class inheritnace from more than one parent or base class.  

**Multilevel Inheritance**
- When a child or drive class become a perent for another child or base class.
***Incase attribute is present in child class than it will take from nearest parent class***

Super()

Super method is used to access the methods of a super class in the drived class & "Super().init() --> call constructor of base class.

Class methods

Class methods are only bound to classes not to objects of class Syntax to create class methods "@classmethod" decorator is used to do this

   class IphonePrice:
      company="Apple"
      price="150k"
      location="Calefornia"
      @classmethod
      def reducePrice(self,newprice):
      self.price=new
  main=IphonePrice()
  print(main.price)     
  main.reducePrice("80k")
  print(main.price)
  print(IphonePrice.price)

@Property Decorators

get output from below written exmaple you can use (data.name) to print the function value which it returns Example

  class Employee:
        @property
         def name(self):
         return self.Name
  data=Employee()
  Name="varinder"
  print(data.name)

@getter or setter

Above mention "@property_decotrstor" is called getter who get the value and with help of setter method or decorator you can define a function+@name.setter like that. Example is connected with above one

  @name.setter
   def name(self,value):
       self.name=value

Operator overloading in Python

Operators can be overloaded by using dunder methods in python.Mostly these methods are called when a given operator is used on the objects. Examples

"add()" --> for add overload
"mul()" --> for multiply overload
"sub()" --> for minus overload
"truediv()" --> for divission overload Some questions solved with inheritance *For more overload perporties click Here