Python Handbook — From Zero to Hero

Table of Contents

1. Python Basics

Variables and Data Types

# Variables
name = "Vaibhav"
age = 25
height = 5.9
is_student = True

# Data Types
print(type(name))    # str
print(type(age))     # int
print(type(height))  # float
print(type(is_student))  # bool

Strings

# String Operations
name = "DSWallah"
print(name.upper())      # DSWALLAH
print(name.lower())      # dswallah
print(name.replace("D", "X"))  # XSWallah
print(name[0:3])         # DSW
print(len(name))         # 8

# f-strings (formatted strings)
name = "Vaibhav"
age = 25
print(f"Hello, I am {name} and I am {age} years old")

Conditional Statements

# if-elif-else
age = 25
if age < 18:
    print("Minor")
elif age < 60:
    print("Adult")
else:
    print("Senior")

# Ternary operator
status = "Adult" if age >= 18 else "Minor"

Loops

# for loop
for i in range(10):
    print(i)

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

# List comprehension
squares = [x**2 for x in range(10)]
print(squares)  # [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

2. Data Structures

Lists

# Lists
fruits = ["apple", "banana", "cherry"]
fruits.append("orange")    # Add to end
fruits.insert(1, "mango")  # Insert at index 1
fruits.remove("banana")    # Remove specific item
fruits.pop()               # Remove last item
print(fruits[0])           # Access by index
print(len(fruits))         # Length

Dictionaries

# Dictionaries
student = {
    "name": "Vaibhav",
    "age": 25,
    "course": "Data Science"
}
print(student["name"])           # Access value
student["email"] = "vaibhav@dswallah.com"  # Add new key
del student["age"]               # Delete key
print(student.keys())           # All keys
print(student.values())         # All values

Sets and Tuples

# Sets (unique elements)
colors = {"red", "blue", "green", "red"}
print(colors)  # {'red', 'blue', 'green'}

# Tuples (immutable)
point = (10, 20)
print(point[0])  # 10

3. Object-Oriented Programming

# Classes and Objects
class Student:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    def introduce(self):
        return f"Hi, I am {self.name} and I am {self.age} years old"

# Create object
student1 = Student("Vaibhav", 25)
print(student1.introduce())

4. NumPy

import numpy as np

# Arrays
arr = np.array([1, 2, 3, 4, 5])
print(arr.mean())    # 3.0
print(arr.std())     # 1.4142135623730951
print(arr.max())     # 5

# 2D Arrays
matrix = np.array([[1, 2, 3], [4, 5, 6]])
print(matrix.shape)  # (2, 3)
print(matrix.T)      # Transpose

5. Pandas

import pandas as pd

# DataFrame
data = {
    "Name": ["Vaibhav", "Rahul", "Priya"],
    "Age": [25, 30, 28],
    "Course": ["Data Science", "AI", "ML"]
}
df = pd.DataFrame(data)

# Operations
print(df.head())           # First 5 rows
print(df.describe())       # Statistics
print(df[df["Age"] > 25])  # Filter
print(df.groupby("Course").mean())  # Group by

6. Matplotlib

import matplotlib.pyplot as plt

# Line plot
x = [1, 2, 3, 4, 5]
y = [2, 4, 6, 8, 10]
plt.plot(x, y)
plt.xlabel("X-axis")
plt.ylabel("Y-axis")
plt.title("Line Plot")
plt.show()

# Bar chart
plt.bar(["A", "B", "C"], [10, 20, 15])
plt.show()

7. Web Scraping

import requests
from bs4 import BeautifulSoup

# Fetch webpage
url = "https://example.com"
response = requests.get(url)

# Parse HTML
soup = BeautifulSoup(response.text, "html.parser")
titles = soup.find_all("h2")
for title in titles:
    print(title.text)

8. Automation

# Email automation
import smtplib

def send_email(to, subject, body):
    server = smtplib.SMTP("smtp.gmail.com", 587)
    server.starttls()
    server.login("your-email@gmail.com", "your-password")
    message = f"Subject: {subject}

{body}"
    server.sendmail("your-email@gmail.com", to, message)
    server.quit()

# File automation
import os
import shutil

# Organize files by extension
for file in os.listdir("downloads"):
    if file.endswith(".pdf"):
        shutil.move(f"downloads/{file}", "pdfs/")
    elif file.endswith(".jpg"):
        shutil.move(f"downloads/{file}", "images/")

9. Python Projects for Resume

10. Python Interview Questions

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