Learn Python Programming

Python String

Strings are immutable sequences of characters. Python provides powerful built-in methods for searching, formatting, splitting, and transforming text.

Creating Strings

# Single or double quotes
name = "Alice"
greeting = 'Hello, World!'

# Multi-line strings
paragraph = """This is
a multi-line
string."""

# Raw strings (no escape processing)
path = r"C:\Users\name\documents"

# f-strings (formatted string literals, Python 3.6+)
age = 25
msg = f"I am {age} years old"
calc = f"2 + 2 = {2 + 2}"

String Indexing and Slicing

s = "Python Programming"

print(s[0])      # "P"
print(s[-1])     # "g"
print(s[0:6])    # "Python"
print(s[7:])     # "Programming"
print(s[::-1])   # "gnimmargorP nohtyP" (reversed)
print(len(s))    # 18

Common String Methods

text = "  Hello, World!  "

# Case methods
print(text.upper())       # "  HELLO, WORLD!  "
print(text.lower())       # "  hello, world!  "
print(text.title())       # "  Hello, World!  "
print(text.capitalize())  # "  hello, world!  "
print(text.swapcase())    # "  hELLO, wORLD!  "

# Whitespace
print(text.strip())       # "Hello, World!"
print(text.lstrip())      # "Hello, World!  "
print(text.rstrip())      # "  Hello, World!"

# Search
print(text.find("World"))      # 9 (index, or -1 if not found)
print(text.count("l"))         # 3
print(text.startswith("  H")) # True
print(text.endswith("!  "))   # True

# Replace and split
print("hello".replace("l", "L"))         # "heLLo"
print("a,b,c".split(","))                 # ["a", "b", "c"]
print(" ".join(["Hello", "World"]))       # "Hello World"

# Check content
print("abc123".isalnum())    # True
print("abc".isalpha())       # True
print("123".isdigit())       # True
print("  ".isspace())        # True

String Formatting

name = "Alice"
score = 95.678

# f-strings (recommended)
print(f"Name: {name}, Score: {score:.1f}")  # "Name: Alice, Score: 95.7"
print(f"{name:>10}")    # right-align in 10 chars
print(f"{name:<10}")    # left-align in 10 chars
print(f"{name:^10}")    # center in 10 chars
print(f"{1000000:,}")   # "1,000,000" (thousands separator)

# .format() method
print("Hello, {}!".format(name))
print("{0} scored {1:.0f}%".format(name, score))

# % formatting (older style)
print("Hello, %s! Score: %.1f" % (name, score))

• Strings are immutable — methods return new strings, they do not modify the original.
• Use f-strings for formatting — they are readable, fast, and the modern standard.
• split() and join() are inverses — use them for string-to-list and list-to-string conversion.
• Use in operator for substring checks: "py" in "python" returns True.
• Raw strings (r"...") are useful for regex patterns and file paths.