BEST PYTHON TUTORIAL FOR BEGINNERS

Best Python Tutorial For beginners

To all Python lovers, here I’m writing an easy tutorial for learning the python programming language.

As you know with the growth in Machine Learning & Artificial Intelligence, the future of the industry will be dependent on AI-based applications. Python is the stepping stone to start your career in automation and data science.

Few real-time application of Python:

1. Web Scraping
2. Image Processing
3. Machine Learning & AI
4. Automate excel & CSV files
5. Scientific & Numeric Computing
6. Email Automation
7. Data Analysis
8. Data Visualization
9. Web Development using Django
10. Gaming development

Benefits of using Python over other programming languages:

• Open Source (No license required to buy software) & supports Community development
• Extensively Support multiple Libraries
• Data Analysis is done using Pandas
• Numerical Calculation is done using NumPy
• Object-Oriented programming language
• Python is easier than C, C++, Java, .Net, etc.
• High-performance speed
• Better productivity
• User-friendly data-structures

All top companies like Google, Facebook, Microsoft, Youtube, Quora, Yahoo, Salesforce are currently using Python.

This tutorial will cover:-

1. Python Installation
2. Python Data Types

• Numbers
• Strings
• List
• Tuple
• Dictionary
• Sets

3. Operators
4. Conditionals Statements
5. Loops
6. Functions
7. File Handling

Python Installation

1. Download python latest version from anaconda.com/download/
2. Complete setup installation
3. Install visual studio code from code.visualstudio.com
4. Start using Jupyter notebook

Variables

Python stores data/ values in memory using a variable. A variable is a name given by you, to which you assign a piece of data that is stored in an area of the computer’s memory, allowing you to refer to that data when you need to later in the program

a = 10
b = 'Welcome to Gyansetu!'
c = 10.11
print(a,b,c)

## output:
## 10 Welcome to Gyansetu! 10.11

Here the variables are a, b, c

Python Data Types

Numbers:

There are 3 types of Numbers:

1. Integer
2. Float
3. Complex
   1. Integer (int): Integer is a non-decimal number formed by the combination of 0 – 9 digits.
   2. Float (float): Afloat is a decimal number that can be represented on a number line.
   3. Complex (complex): They are numbers that consist of an imaginary number and a real number.

Different types of numbers

a = 10   #integer
b = 43.49     #float
c = 1 + 2j       #complex

 To accept values from user input

x = input("Enter any number : ")
y = input("Enter any number : ")
z = input("Enter any number : ")
print(x,y,z)

## output:
## Enter any number : 2
## Enter any number : 3
## Enter any number : 1
## 2 3 1

To know the type of data:

print(type(x))
print(type(y))
print(type(z))
## output:
## 
## 
## 

String

A string in Python consists of a series or sequence of characters – letters, numbers, and special characters.

Strings can be indexed – often synonymously called subscripted as well. Similar to C, the first character of a string has the index 0.

How to print a string

a = "sahil"
b = 20
c = 30
print("%d-%d-%d" % (a,b,c))

## output:

## This will give error because %d is used in print for a and a is a string, %d is used for integer values

### Another way to solve the error

a = "sahil"
b = 20
c = 30
print("%s-%d-%d" % (a,b,c))
## output:
## sahil-20-30
## %s is used for string values

How to print a string using .format

a = "sahil"
b = 20
c = 30
print("{}-{}-{}".format(a,b,c))
## output:
## sahil-20-30

Indexing in Python:

Indexing # starts from 0 to n – 1 where n is the length of string use []

Example to understand indexing:

s = "Hello World!"
print(s[2])
print(s[6])
## output:
## l
## s

Slicing in Python:

Slicing # used to make sub-strings from strings used with start, end and step variable

# s[start:end:step]
s = "Hello World!"
x = s[3:11]
y =  s[:]
z = s[:6]
p = s[6:]
print(x)
print(y)
print(z)
print(p)
print(s)
## output:
## lo World
## Hello World!
## Hello
## World!
## Hello World!

Basic String Functions: –

swapcase, upper, lower, strip, lstrip, rstrip, find, replace, format, center

Swapcase:- used to change uppercase letters into lowercase letters and vice versa

Upper:- It changes all letters into uppercase and returns the string

Lower:- It changes all letters into lowercase and return the string

Strip:- strip is used to remove all leading and trailing spaces from the string

Lstrip:- It is used to remove left space

Rstrip:- It is used to remove the right space

Example to understand string functions:

s = input("Enter a String : ")
print(s)
print("Swapcase : ",s.swapcase())
print("Upper : ",s.upper())
print("Lower : ",s.lower())
print("Strip : ",s.strip())
print("LStrip : ",s.lstrip())
print("RStrip : ",s.rstrip())
## output:
## Enter a String : iclass gyansetu
## iclass gyansetu
## Swapcase :  ICLASS GYANSETU
## Upper :  ICLASS GYANSETU
## Lower :  iclass gyansetu
## Strip :  iclass gyansetu
## LStrip :  iclass gyansetu
## RStrip :  iclass gyansetu

Lists

• Lists are one of the most powerful tools in Python.
• They are just like the arrays declared in other languages.
• But the most powerful thing is that list need not be always homogeneous.
• A single list can contain strings, integers, as well as objects.
• Lists can also be used for implementing stacks and queues.
• Lists are mutable, i.e., they can be altered once declared.

Declaring a list:

L = [1, "a" , "string" , 1+2]
print(L)
## output : [1, 'a', 'string', 3]

Homogeneous & Non-Homogeneous List

Homogeneous List contains all elements of same data type.

Non- Homogeneous List contains elements of different data type.

l = [ 'hello','hi','how are you' ]
print(l)
print(l[2])
l = [ 56,23,45,12,67,12,43,1,6,8,6,33,12]
print("Homogeneous List :",l)
print(l[5])
l = [ 'hello','hi', 3, 4.5 ]
print("Non-Homogeneous List : ",l)
print(l[-3])
## output:
## ['hello', 'hi', 'how are you']
## how are you
## Homogeneous List : [56, 23, 45, 12, 67, 12, 43, 1, 6, 8, 6, 33, 12]
## 12
## Non-Homogeneous List :  ['hello', 'hi', 3, 4.5]
## hi

Tuple

• A Tuple is a collection of Python objects separated by commas.
• In someway a tuple is similar to a list in terms of indexing, nested objects, and repetition but a tuple is immutable, unlike lists which are mutable.

Declaring a Tuple

tup = 'python', 'gyansetu'
print(tup)  
## output: ('python', 'gyansetu')

### Another way for doing the same
tup = ('python', 'gyansetu')
print(tup)
## output: ('python', 'gyansetu')

Dictionary

• It consists of key-value pairs.
• The value can be accessed by a unique key in the dictionary.

Dictionary Example with Key-Value pair

mydict = {
    'name':'python',
    'build_year':1991,
    'Father of Python':"Guido Van Rossum",
    'Frame_works':['Django','Flask','Web2PY','Torando','kivi'],
    'versions' : [1.0,2.0,3.0],
    'latest_version':3.6}
print(mydict)
print("Name : ", mydict['name']) #returns the value of the key 'name'
print("Frame Works : ", mydict['Frame_works'])
## output:
## {'name': 'python', 'build_year': 1991, 'Father of Python': 'Guido Van Rossum', 'Frame_works': ['Django', 'Flask', 'Web2PY', 'Torando', 'kivi'], 'versions': [1.0, 2.0, 3.0], 'latest_version': 3.6}
## Name :  python
## Frame Works :  ['Django', 'Flask', 'Web2PY', 'Torando', 'kivi']

Operators in Python

Arithmetic Operators

Arithmetic operators are used to performing mathematical operations like addition, subtraction, multiplication and division

1. Addition Operator ( + )
2. Subtraction Operator ( – )
3. Multiplication Operator ( * )
4. Division Operator ( / )
5. Modulas Operator ( % )
6. Floor Division ( // )
7. Exponent Operator ( ** )

Example of Arithmetic Operator

x = 10
y = 3
z1 = x+y
z2 = x-y
z3 = x * y
print("Addition of {} and {} is {}.".format(x,y,z1))
print("Subtraction of {} and {} is {}.".format(x,y,z2))
print("Multiplication of {} and {} is {}.".format(x,y,z3))
## output:
## Addition of 10 and 3 is 13.
## Subtraction of 10 and 3 is 7.
## Multiplication of 10 and 3 is 30.

Comparison Operators

These operators compare the values on either side of them and decide the relation among them.

1. Less Than ( < )
2. Less Than Equals To ( <= )
3. Greater Than ( > )
4. Greater Than Equals To ( >= )
5. Equals To Equals To ( == )
6. Not Equals To ( != )

Example of Comparison Operator

#returns true if statement is True else returns False

print("6 < 8 ", 6 < 8)               ## output: True
print("6 <= 6 ", 6 <= 6)             ## output: True
print("5 > 6 ", 5 > 6)               ## output: False
print("6 != 7 ", 6 != 7)             ## output: True

Logical Operators

Logical operators are used on conditional statements (either True or False). They perform Logical AND, Logical OR, and Logical NOT operations

1. And

If x is false, return x

else return y

2. Or

If x is false, return y

else x

Examples:

print( 5>7 and 6-5*3+6)                   ## output: False
print( 6-4*3+6 and 5>7)                   ## output: 0
print( 6-4*3+6 or 6 > 5)                  ## output: True
print( 6 > 5 or 6-4*3+6)                  ## output: True

Membership Operator

Membership operators are operators used to validate the membership of a value. It tests for membership in a sequence, such as strings, lists, or tuples.

1. in
2. not in

Examples:

s2 = "Dog is an animal."
s1 = "Dog"
x = s1 in s2
if x :
    print("Pattern Found in step 1") #return this if x=True
else :
    print("Patten Not Found")
p = s1 not in s2
print(x)
print(p)
## OUTPUT:
## Pattern Found in step 1
## True
## False

Identity Operator

Python Membership and Identity Operators · in operator: The ‘in’ operator is used to check if a value exists in a sequence or not.

1. is
2. is not

Examples:

x = 5
y = 5
print(x is y)
print( x is not y )
p = 3
q = 4
if p is q :
    print("Both are equal")
else :
    print("Both are different")

Conditional Statements

In programming and scripting languages, conditional statements or conditional constructs are used to perform different computations or actions depending on whether a condition evaluates to true or false. (Please note that true and false are always written as True and False in Python.)

Example to calculate the greatest of 3 numbers using a conditional statement

#Greatest among Three numbers
a = int(input("A : "))
b = int(input("B : "))
c = int(input("C : "))
if a >= b :
    if a >= c :
        print("A is greatest ")
    else :
        print("C is greatest ")
elif b >= c :
    print("B is Greatest")
else :
    print("C is Greatest ")
## OUTPUT:
## A : 12
## B : 32
## C : 16
## B is Greatest

Loops in Python

Loops can be divided into 2 kinds.

• Finite: This kind of loop works until a certain condition is met
• Infinite: This kind of loop works infinitely and does not stop ever.

There are 2 kinds of loops:

• for
• while

For Loops: These loops are used to perform a certain set of statements for a given condition and continue until the condition has failed. You know the number of times that you need to execute the for a loop.

Example of For loop

print("List Iteration")
l = ["books", "bags", "pens"]
for i in l:
    print(i)
## OUTPUT:
## List Iteration
## books
## bags
## pens

For loop using range()

for i in range(5):
print(i)
## OUTPUT:
## 0
## 1
## 2
## 3
## 4

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