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
  1. Operators
  2. Conditionals Statements
  3. Loops
  4. Functions
  5. 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

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:

python strings

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

  1. 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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