Python Notes for B-Tech , Bsc , Bca....

 

UNIT-1

What is Python?

* Python is a high level , general purpose object oriented programming language.

* It was created by Guido Van Rossum in 1991 at CWI in Netherland.

Syntex-

print("Hello")

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Features of Python:-

* Simple and easy to learn

* Open source

* Platform independent

* Rich Library

* Portable

* Interpreted

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Applications of  Python :-

* Web development

* Game development

* IOT development

* AI

* Machine Learning

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# Input / Output :- 

* For taking input in python , we have input()

*  For taking output in python , we have print()

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Python Comments :- Comments are nothing but ignorable part of python program that are ignored by the interpreter.

There are 2 types of Comments -

1. Single line comment

syntex- #..........

2. Multi line comment

syntex- ''' ..........

..........

........

'''

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Keywords:- Keywords are the words whose meaning is already being defined in Python interpreter.

* Python keywords are Case sensitive.

* We cant use a keywords as a variable name, method name or any other identifiers.

* Total 33 keywords in Python.

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Data Type:- Data Type represent the different kinds of values that we stored on the variable.

* Basic data type in python:-

1. Number

2. String

3. dict

4. set

5. List

6. tuple

* We do not need to specify the data type explicitly , based on value types allocated automatically.

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Variable :- Variable is the name of memory location where we can store different type of values.

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Python Interpreter:- A python interpreter is a computer program that convert each high-level program statement into machine code.

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Python Shell:- The python shell is the interpreter that executes your Python program , other piece of Python code or simple commands.

It is also used to execute a single Python commands and display the result.

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Python Identation:- It refers to adding white space before a statement to a particular block of code. In another words a, all the statement with the same space to the right , belong to the same code block.

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Literals:- Literals are constant values assigned to constant variable. It represent fixed values that cannot be modified.

* We mainly have five types of literals which includes string literals, numeric literals, boolean literals, literal collections and a special literal None.

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Python Operators:- They are used to perform operations on values and variable.

Types :-

1) Arithmetic Operator- They are used to perform operations on values and variables.

example :  + , - , *  , /

2) Logical Operator- They perform LogicalAnd , LogicalOr and LogicalNot operations. They are used to combine conditional statement. 

example : OR , NOT , AND.

3) Bitwise Operator- They act on bits and perform the bit-by-bit operations. They are used to operate on binary number.

example: & , >> , << , | etc .

4) Assignment Operator- They are used to assign values.

example: = , += , -= , etc.

5) Relational Operator- They are used to compare the operand values. 

example: == , > , < , etc

6) Ternary Operator- It allows us to evaluate if a condition is true or false.

example: if , else .

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UNIT-2

Flow Control:- Flow Control describe the order in which statement will be executed at runtime.

1. Conditional Statement-

 👉 if statement -

syntex - if condition :

statement

👉 if else - 

syntex- if condition:

statement

else:

statement

👉else if

syntex- if condition:

statement

elif condition:

statement

else:

statement

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Example of else if ::

age = int (input ("Enter your age: "))

if age<18 :  

    print('You are too young to marry')

elif age>60:

    print('You are too old to marry')

else:

    print("we will find a perfect match for you")

output ~

Enter your age: 25

We will find a perfect match for you

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2. Iterative statement-

👉 for loop

syntex- for var-name in range(start,end):

statement

Example of for loop:-

table = int(input("Enter a number : "))

for number in range(1,11):

      print(table * number)

output~

Enter a number : 6

6     12    18    24    30    36    42    48    54    60

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👉 while loop

syntex- while condition:

statement

    Example of while loop-

password = "vaibhav"

input_password = input ("enter password :")

while password != input_password:

            input_password = input("enter password :")

else :

       print("unloacked !! ")

output~ 

Enter password :vaibhav

unlocked !!

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3. Loop control statement -

👉Continue statement

example- 

for num in range(1,11):

    if num % 2 == 0 :

        continue

   else:

        print(num)

output~

1     3     5     7     9

👉break statement

example - 

for num in range(1,11) :

    if num % 2 == 0:

        break

   else:

        print(num)

output~

1       

 👉pass: The pass statement is used as a placeholder for future code. When the pass statement is executed , nothing happen but you avoid getting an error when empty code is not allowed.

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UNIT-3

List:- List is a data structure which is also called collection of items, in which we can store anything like-string, float , integer.

syntex-              list-name=[item1 , item2, ......... , item n ]

Note- * We write the item of the list inside "square brackets" ([]) and each item is seperated by "commas" (,).

* Duplicate are allowed.

* Mutable in nature.

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Program to print using indexing :-

list1 = [10, 'vaibhav' , true , 10.5 ,  'bhatnagar' ,  10]

print(list1[2])

output~      [true]

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Program to print by slicing :-

list2 = [10 , 'vaibhav' , true , 10.5 , 10]

print( list2[1:4] )

output~   [ 'vaibhav' , true , 10.5]

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Count method () : Count () is a Python in-built function that returns the number of times an object appears in a list.

Example-  

list2=[10 , 'vaibhav' , true , 10.5 , 10]

print(list2.count(10))

output: 2

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index method () : It return the position at the first occurence of the specified value.

Example- list2 = [10 , 'vab' 20 , 13.5 , 30 ]

print(list2.index(30))

output- 4

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insert method () : It insert the specified value at the specified position.

Example- 

list3= [10 , 'vab' , 30 , 40.5]

list3.insert(3 , "Hello")

print(list3)

output- [10 , 'vab' , 30 , 'Hello' , 40.5]

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pop method () : It is used to delete the element from the specified position.

Example- 

list4= [10 , 'vab' , 30]

list4.pop(2)

print(list4)

output- [10 , 'vab']

* IF WE DOES NOT GIVE INDEX POSITION THAN BY DEFAULT IT WILL DELETE LAST ELEMENT

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Python Tuple:- It is a data structure which is also called Collection of items , in which we can store anything like string , float , integers.

Syntex: tuple-name=(item 1 , item 2 , ..... item n)

Note- * We write the item of the tuple inside parathesis "()" and each item is seperated by comma ",".

* Duplicates are allowed.

* Immutable in Nature.

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Set:- Set is a data structure which is also called collection of items in which we can represent a group of unique value as a single entity.

Syntex: set-name={item 1 , item 2 , .......item n }

* We write the item of set inside the curly braces "{}" .

* Insertion order is not preserved.

* Indexing and slicing not safe.

* Hetrogenous element are allowed.

* Mutable in Nature.

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Dictionary:- Dictionary is a data structure in which we represent a group of object as key-value pair.

syntex: dict_name = {"key": "value"}

Note-

* Insertion order is preserved.

* Indexing and slicing not work.

* Hetrogenous element are allowed.

* Mutable in nature.

* Key must be unique , but duplicates value are allowed.

Create Empty Dict:- 

var=dict()

print(type(var))

or

var = {}

print(type(var))

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