Python Tutorial

1. Basic Syntax

Hello World:

print("Hello, World!")

Variables:

x = 5
name = "Alice"

Data Types:

Python has various built-in data types, such as:

• Integer (int)
• Float (float)
• String (str)
• Boolean (bool)

x = 5  // int
y = 3.14  // float
name = "John"  // str
is_active = True  // bool

2. Control Flow

If Statements:

x = 10
if x > 5:
print("x is greater than 5")
elif x == 5:
print("x is equal to 5")
else:
print("x is less than 5")

For Loops:

// Iterate through a range
for i in range(5):
print(i)

// Iterate through a list
names = ["Alice", "Bob", "Charlie"]
for name in names:
print(name)

While Loops:

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

Break and Continue:

for i in range(10):
if i == 5:
  break  // exit the loop
if i == 3:
  continue  // skip the rest of the loop and continue
print(i)

3. Functions

Defining Functions:

def greet(name):
print(f"Hello, {name}!")

greet("Alice")

Returning Values:

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

result = add(3, 4)
print(result)  // Outputs: 7

Keyword Arguments:

def person_info(name, age):
print(f"Name: {name}, Age: {age}")

person_info(age=30, name="John")

4. Data Structures

Lists (ordered, mutable):

fruits = ["apple", "banana", "cherry"]
fruits.append("date")  // Adds an element to the list
print(fruits[1])  // Access element by index (starts at 0)

Tuples (ordered, immutable):

coordinates = (4, 5)
print(coordinates[0])  // Access element by index

Dictionaries (unordered, key-value pairs):

person = {"name": "Alice", "age": 25}
print(person["name"])  // Access value by key

Sets (unordered, no duplicates):

numbers = {1, 2, 3, 4, 5}
numbers.add(6)  // Adds an element
print(numbers)

5. List Comprehensions

List Comprehensions allow you to create lists in a more compact and readable way.

squares = [x ** 2 for x in range(5)]
print(squares)  // Outputs: [0, 1, 4, 9, 16]

Conditional List Comprehension:

even_numbers = [x for x in range(10) if x % 2 == 0]
print(even_numbers)  // Outputs: [0, 2, 4, 6, 8]

6. Object-Oriented Programming (OOP)

Defining a Class:

class Dog:
def __init__(self, name, age):
  self.name = name
  self.age = age

def bark(self):
  print(f"{self.name} says woof!")

dog1 = Dog("Rex", 3)
dog1.bark()  // Outputs: Rex says woof!

Inheritance:

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

def speak(self):
  print(f"{self.name} makes a sound")

class Dog(Animal):
def speak(self):
  print(f"{self.name} barks")

dog = Dog("Buddy")
dog.speak()  // Outputs: Buddy barks

7. File Handling

Opening and Reading Files:

// Open file and read content
with open("example.txt", "r") as file:
content = file.read()
print(content)

Writing to Files:

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

Appending to Files:

with open("output.txt", "a") as file:
file.write("\nAppended text.")

8. Error Handling

Try-Except Blocks:

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

Finally Block (for cleanup):

try:
file = open("data.txt", "r")
// Some operations
except FileNotFoundError:
print("File not found")
finally:
file.close()

9. Libraries and Modules

Importing a Module:

import math
print(math.sqrt(16))  // Outputs: 4.0

Importing Specific Functions:

from math import sqrt
print(sqrt(16))  // Outputs: 4.0

Creating a Module:

// mymodule.py
def greet(name):
return f"Hello, {name}!"

// Another script
import mymodule
print(mymodule.greet("Alice"))  // Outputs: Hello, Alice!

10. Decorators

Function Decorators:

def decorator(func):
def wrapper():
  print("Before function call")
  func()
  print("After function call")
return wrapper

@decorator
def say_hello():
print("Hello!")

say_hello()

11. Lambda Functions

Anonymous Functions:

add = lambda x, y: x + y
print(add(2, 3))  // Outputs: 5

12. Iterators and Generators

Creating an Iterator:

class Counter:
def __init__(self, low, high):
  self.current = low
  self.high = high

def __iter__(self):
  return self

def __next__(self):
  if self.current > self.high:
    raise StopIteration
  else:
    self.current += 1
    return self.current - 1

counter = Counter(1, 3)
for num in counter:
print(num)

Generators:

def count_up_to(max):
count = 1
while count <= max:
  yield count
  count += 1

gen = count_up_to(3)
for number in gen:
print(number)

13. Regular Expressions

Using the re module:

import re
pattern = r"\d+"  // Matches one or more digits
text = "The number is 42"
match = re.search(pattern, text)
if match:
print(match.group())  // Outputs: 42

14. Working with Dates and Times

Datetime module:

import datetime

now = datetime.datetime.now()
print(now)  // Outputs: current date and time

date_str = "2025-03-08"
date_obj = datetime.datetime.strptime(date_str, "%Y-%m-%d")
print(date_obj)  // Outputs: 2025-03-08 00:00:00

15. Virtual Environments

Creating a Virtual Environment:

python -m venv myenv

Activating the Virtual Environment:

Windows:

myenv\Scripts\activate

Mac/Linux:

source myenv/bin/activate

Deactivating:

deactivate