Python Programming Guide

This guide covers fundamental Python concepts with examples. Each section includes code samples and explanations.

Table of Contents

1. Hello World
2. Strings
   • Single vs Double Quotes
   • Multiline Strings
   • String Operations
   • String Methods
   • String Formatting

Hello World

Basic "Hello World" program implementation can be found in 01-hello-world.py.

Strings

Single vs Double Quotes

When working with strings containing apostrophes, you have two options:

1. Using escape characters:

# Using escape character
text = 'Viswa\'s World'

2. Using double quotes (recommended):

# Better approach
text = "Viswa's World"

Multiline Strings

Python supports multiline strings using triple double quotes:

"""Viswa's World was fantastic 
in the 1990's"""

String Operations

Length Function

message = "Hello World"
print(len(message))  # Get string length

String Indexing

message = "Hello World"
print(message[10])  # Outputs: 'd'

String Slicing

message = "Hello World"
print(message[0:5])  # Outputs: 'Hello'

String Methods

Case Conversion

message = "Hello World"
print(message.upper())  # Convert to uppercase
print(message.lower())  # Convert to lowercase

Count and Find

message = "Hello World"
print(message.count('l'))    # Outputs: 3 (counts occurrences of 'l')
print(message.find('World')) # Outputs: 6 (index where 'World' starts)

Replace

message = "Hello World"
message = message.replace('World', 'Python')
print(message)  # Outputs: 'Hello Python'

String Formatting

Basic String Concatenation

greeting = "Hello"
name = "Viswa"
message = greeting + ', ' + name + '. Welcome'
# Outputs: 'Hello, Viswa. Welcome'

Format Method

greeting = "Hello"
name = "Viswa"
message = '{}, {}. Welcome!'.format(greeting, name)
# Outputs: 'Hello, Viswa. Welcome!'

F-Strings (Python 3.6+)

greeting = "Hello"
name = "Viswa"
message = f'{greeting}, {name.upper()}. Welcome!'
# Outputs: 'Hello, VISWA. Welcome!'

Additional Information

• Use dir() function to view all available string methods and attributes
• Methods are similar to functions but are associated with objects

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Note: This guide is continuously updated with new Python concepts and examples.

greeting = "Hello" name = "Viswa" print(dir(name))

Output: ['add', 'class', 'contains', 'delattr', 'dir', 'doc', 'eq', 'format', 'ge',] etc.

Using help(str) function to access a lot more info about string methods

greeting = "Hello" name = "Viswa" print(help(str.lower))

Output: lower(self, /) Return a copy of the string converted to lowercase.

3. Integers & Floats

Arithmetic Operations

1. Addition: 3 + 2
2. Subtraction: 3 - 2
3. Multiplication: 3 * 2
4. Division: 3 / 2
5. Floor Division: 3 // 2
6. Exponent: 3 ** 2
7. Modulus: 3 % 2

Comparision Operator

1. Equal: 3 == 2
2. Not Equal 3 != 2
3. Greater Than: 3 > 2
4. Less Than: 3 < 2
5. Greater than or Equal: 3 >= 2
6. Less or Equal: 3 <= 2

Lists

lists are mutable in python. we can add, remove and change the position etc.

courses = ['history', 'physics', 'maths', 'science']

print the courses list

print(courses) Output: ['history', 'physics', 'maths', 'science']

print the values by using length function

print(len(courses)) Output: 4

print the courses by using index i.e (index will start from 0)

print(courses[2]) Output: maths

print the negitive index i.e(the negitive item always be last item in the list)

print(courses[-1]) Output: science

print the out of range of index and check

print(courses[4]) Output: IndexError: list index out of range

print the range of values

print(courses[0:2]) Output: ['history', 'physics']

print the range of values i.e (it's should be assume it's starts from begining same result as above)

print(courses[:2]) Output: ['history', 'physics']

print the range of values i.e (it's should start from 2 and all the way to end)

print(courses[2:]) Output: ['maths', 'science']

list methods i.e (it's added in the end of the list)

courses = ['history', 'physics', 'maths', 'science'] courses.append('arts') print(courses)

Output: ['history', 'physics', 'maths', 'science', 'arts']

list methods by using insert i.e it's should be placed in first since we have added 0

courses = ['history', 'physics', 'maths', 'science'] courses.insert(0, 'arts') print(courses)

Output: ['arts', 'history', 'physics', 'maths', 'science']

list methods by using extend method

courses = ['history', 'physics', 'maths', 'science'] courses_2 = ['arts', 'education']

courses.insert(0, courses_2) print(courses)

Output: [['arts', 'education'], 'history', 'physics', 'maths', 'science']

One more xample for extend method i.e (from actual list and extend list)

courses = ['history', 'physics', 'maths', 'science'] courses_2 = ['arts', 'education']

courses.insert(0, courses_2) print(courses[0])

Output: ['arts', 'education']

One more example of extend method

courses = ['history', 'physics', 'maths', 'science'] courses_2 = ['arts', 'education']

courses.extend(courses_2) print(courses)

Output: ['history', 'physics', 'maths', 'science', 'arts', 'education']

remove some items form the list by using remove method

courses = ['history', 'physics', 'maths', 'science'] courses.remove('maths') print(courses)

Output: ['history', 'physics', 'science']

Use pop method to remove the items form list

courses = ['history', 'physics', 'maths', 'science'] courses.pop() print(courses)

Output: ['history', 'physics', 'maths']

Use reverse method to list the items

courses = ['history', 'physics', 'maths', 'science'] courses.reverse() print(courses)

Output: ['science', maths', 'physics', 'history',]

Use sort method it will trigger alphabitical order

courses = ['history', 'physics', 'maths', 'science'] courses.sort() print(courses)

Output: ['history', 'maths', 'physics', 'science']

Sort method by using numbers i.e(Ascending order)

numbers = [1, 7, 3, 5, 2] numbers.sort() print(numbers)

Output: [1, 2, 3, 5, 7]

Tuples

Tuples are immutable in python. tuples are exactly the same as lists, but instaed of using squre braces [] use Parentheses ()

Example: tuple_1 = ('history', 'physics', 'maths', 'science')

tuples usecase

tuple_1 = ('history', 'physics', 'maths', 'science') tuple_2 = tuple_1

print(tuple_1) print(tuple_2)

Output: ('history', 'physics', 'maths', 'science') ('history', 'physics', 'maths', 'science')

tuples are immutable

tuple_1 = ('history', 'physics', 'maths', 'science') tuple_2 = tuple_1

print(tuple_1) print(tuple_2)

tuple_1[0] = 'art'

print(tuple_1) print(tuple_2)

Output: TypeError: 'tuple' object does not support item assignment, beacuse tuple is immutable