📍 String Indexing & Slicing — Extract What You Need

Learn to pinpoint and extract specific characters and portions of strings using indexing and slicing.

🎯 String Indexing

Indexing means accessing a single character at a specific position. Python uses zero-based indexing (first character is at position 0):

word = "Python"
print(word[0])   # P
print(word[1])   # y
print(word[2])   # t
print(word[5])   # n

💡 Negative Indexing

Python allows negative indices to count backward from the end. `-1` is the last character, `-2` is second-to-last, etc.:

word = "Python"
print(word[-1])   # n (last char)
print(word[-2])   # o (second to last)
print(word[-6])   # P (first char)

🎨 String Slicing

Slicing extracts a substring using the syntax `string[start:end:step]`. The `end` position is exclusive (not included):

sentence = "Hello World"

# Basic slicing
print(sentence[0:5])      # Hello
print(sentence[6:11])     # World
print(sentence[0:5:1])    # Hello (explicit step)

# Omitting positions
print(sentence[:5])       # Hello (from start)
print(sentence[6:])       # World (to end)
print(sentence[:])        # Hello World (entire string)

🔑 Slicing with Steps

The third parameter controls how many positions to skip each time:

text = "Python"
print(text[::2])    # Pto (every 2nd char)
print(text[1::2])   # yhn (starting from index 1, every 2nd)
print(text[::-1])   # nohtyP (reverse!)

numbers = "0123456789"
print(numbers[::3]) # 0369

📊 Indexing & Slicing Reference

💡 Common Patterns

# Get first word from sentence
sentence = "Python is awesome"
first_word = sentence[:6]  # Python

# Get last 5 characters
filename = "document.txt"
extension = filename[-4:]  # .txt

# Get middle portion
code = "a1b2c3d4"
middle = code[2:6]  # b2c3

🔑 Key Takeaways

🔗 What's Next?

Now that you can extract parts of strings, learn string methods that transform them.

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