Python - Review of Python Basics

Review of Python Basics

Python is a versatile and beginner-friendly programming language known for its clean syntax and readability. It is widely used across various domains including web development, data science, automation, and artificial intelligence. This document provides a comprehensive review of Python basics to help reinforce your understanding of its core principles.

Introduction to Python

What is Python?

Python is a high-level, interpreted programming language developed by Guido van Rossum and released in 1991. It supports multiple programming paradigms and emphasizes code readability with significant whitespace (indentation).

Key Features of Python

• Simple and readable syntax
• Large standard library and third-party modules
• Open source and community-driven
• Platform-independent
• Extensive support for integration with other languages and tools

Python Syntax Basics

Printing Output

print("Hello, World!")

Comments

# This is a single-line comment

Multiline Comments

"""
This is a
multi-line comment
"""

Indentation

Indentation is used to define blocks of code:

if True:
    print("This is indented")

Variables and Data Types

Declaring Variables

x = 5
name = "Alice"
is_active = True

Basic Data Types

• int - Integer numbers
• float - Floating-point numbers
• str - String text
• bool - Boolean values (True/False)

Type Conversion

int("10")       # 10
float("5.5")    # 5.5
str(100)        # "100"

Operators

Arithmetic Operators

a + b    # Addition
a - b    # Subtraction
a * b    # Multiplication
a / b    # Division
a % b    # Modulus
a ** b   # Exponentiation
a // b   # Floor division

Comparison Operators

a == b
a != b
a > b
a < b
a >= b
a <= b

Logical Operators

a and b
a or b
not a

Control Flow Statements

If-Else Statement

x = 10
if x > 0:
    print("Positive")
elif x == 0:
    print("Zero")
else:
    print("Negative")

While Loop

count = 0
while count < 5:
    print(count)
    count += 1

For Loop

for i in range(5):
    print(i)

Loop Control

• break – Terminates the loop
• continue – Skips the current iteration
• pass – Does nothing, a placeholder

Functions

Defining and Calling a Function

def greet(name):
    print("Hello", name)

greet("Alice")

Return Statement

def add(a, b):
    return a + b

Default Parameters

def greet(name="Guest"):
    print("Hello", name)

greet()

Data Structures

Lists

fruits = ["apple", "banana", "cherry"]
print(fruits[0])
fruits.append("orange")

Tuples

coordinates = (10, 20)
print(coordinates[1])

Dictionaries

student = {"name": "Alice", "age": 20}
print(student["name"])
student["age"] = 21

Sets

unique_numbers = {1, 2, 2, 3}
print(unique_numbers)  # Output: {1, 2, 3}

String Operations

Common String Methods

text = "hello"
print(text.upper())      # HELLO
print(text.replace("h", "y"))  # yello

Formatted Strings

name = "Alice"
age = 25
print(f"My name is {name} and I am {age} years old.")

Exception Handling

Using try-except

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero.")

Using finally

try:
    f = open("file.txt")
except FileNotFoundError:
    print("File not found.")
finally:
    print("This block always runs.")

Modules and Packages

Importing Standard Modules

import math
print(math.sqrt(16))

Creating a Module

Save as my_module.py: 

def greet():
    print("Hello from module!")

Then import and use it:

import my_module
my_module.greet()

File Handling

Reading a File

with open("sample.txt", "r") as file:
    content = file.read()
    print(content)

Writing to a File

with open("output.txt", "w") as file:
    file.write("Hello, file!")

Object-Oriented Programming

Creating Classes

class Person:
    def __init__(self, name):
        self.name = name

    def greet(self):
        print("Hi, I'm", self.name)

p = Person("Alice")
p.greet()

Inheritance

class Student(Person):
    def __init__(self, name, major):
        super().__init__(name)
        self.major = major

s = Student("Bob", "Mathematics")
s.greet()

Conclusion

These Python basics form the foundation for more advanced topics in programming. Understanding data types, functions, loops, and OOP concepts in Python is essential to progress in domains like machine learning, web development, automation, and scripting. Continue practicing with small projects to enhance your coding skills and deepen your understanding.