Strings and String Methods

Strings are one of the most commonly used data types in Python. A string is a sequence of characters enclosed in quotes. Python provides a rich set of methods for working with text — searching, slicing, formatting, and transforming.

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Creating Strings

# Single quotes
greeting = 'Hello, World!'

# Double quotes
message = "Python is fun!"

# Triple quotes — multi-line strings
paragraph = """This is a
multi-line string that
spans three lines."""

# Triple single quotes also work
another = '''Same thing
with single quotes.'''

print(greeting)
print(paragraph)

Use double quotes when your string contains an apostrophe, and single quotes when it contains double quotes:

sentence = "It's a beautiful day."
html = '<div class="container">Hello</div>'

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String Indexing

Every character in a string has a position (index), starting from 0:

word = "Python"
#       P y t h o n
#       0 1 2 3 4 5
#      -6-5-4-3-2-1

print(word[0])    # P — first character
print(word[5])    # n — last character
print(word[-1])   # n — last character (negative indexing)
print(word[-2])   # o — second-to-last

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String Slicing

Extract a portion of a string using [start:stop:step]:

text = "Hello, World!"

print(text[0:5])    # Hello — characters 0 to 4
print(text[7:12])   # World — characters 7 to 11
print(text[:5])     # Hello — from the start
print(text[7:])     # World! — to the end
print(text[::2])    # Hlo ol! — every 2nd character
print(text[::-1])   # !dlroW ,olleH — reversed string

Key rule: The stop index is exclusive — the character at that position is NOT included.

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String Length

Use len() to get the number of characters:

message = "Hello!"
print(len(message))  # 6

empty = ""
print(len(empty))    # 0

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String Concatenation and Repetition

# Concatenation with +
first = "Hello"
second = "World"
combined = first + ", " + second + "!"
print(combined)  # Hello, World!

# Repetition with *
line = "-" * 40
print(line)  # ----------------------------------------

# You cannot concatenate strings and numbers directly
age = 25
# print("I am " + age)  # TypeError!
print("I am " + str(age))  # I am 25

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String Methods

Python strings have many built-in methods. Here are the most important ones:

Case Methods

text = "Hello, World!"

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!

Searching

text = "Hello, World! Hello, Python!"

print(text.find("World"))       # 7 — index of first occurrence
print(text.find("Java"))        # -1 — not found
print(text.index("World"))      # 7 — like find() but raises ValueError if not found
print(text.count("Hello"))      # 2 — number of occurrences
print(text.startswith("Hello")) # True
print(text.endswith("Python!")) # True
print("World" in text)          # True — membership test

Stripping Whitespace

messy = "   Hello, World!   "

print(messy.strip())   # "Hello, World!" — both sides
print(messy.lstrip())  # "Hello, World!   " — left only
print(messy.rstrip())  # "   Hello, World!" — right only

# Strip specific characters
url = "///path/to/file///"
print(url.strip("/"))  # "path/to/file"

Replacing

text = "Hello, World!"