String Methods Cheatsheet¶

Quick reference for working with strings in Python.

String Literals¶

s = "double quotes"
s = 'single quotes'
s = """multi-line
string"""
s = r"raw string \n not escaped"  # Raw string (backslashes literal)
s = f"formatted {variable}"       # f-string (Python 3.6+)

Indexing and Slicing¶

s = "Hello"
s[0]      # 'H' (first character)
s[-1]     # 'o' (last character)
s[1:4]    # 'ell' (characters 1 to 3)
s[:3]     # 'Hel' (first 3 characters)
s[2:]     # 'llo' (from character 2 to end)
s[::2]    # 'Hlo' (every 2nd character)
s[::-1]   # 'olleH' (reversed)

F-Strings (Preferred)¶

name = "Alice"
age = 30

# Basic
f"{name} is {age}"  # Alice is 30

# Expressions
f"{2 + 2}"  # 4
f"{name.upper()}"  # ALICE

# Formatting
f"{3.14159:.2f}"  # 3.14 (2 decimal places)
f"{1000:,}"  # 1,000 (with thousands separator)
f"{value:>10}"  # Right-aligned in 10 characters

Common String Methods¶

Method	Example	Result
`lower()`	`"HELLO".lower()`	`"hello"`
`upper()`	`"hello".upper()`	`"HELLO"`
`capitalize()`	`"hello".capitalize()`	`"Hello"`
`title()`	`"hello world".title()`	`"Hello World"`
`strip()`	`" hello ".strip()`	`"hello"`
`lstrip()`	`" hello ".lstrip()`	`"hello "`
`rstrip()`	`" hello ".rstrip()`	`" hello"`
`replace(old, new)`	`"hello".replace("l", "L")`	`"heLLo"`
`split(sep)`	`"a,b,c".split(",")`	`["a", "b", "c"]`
`join(iterable)`	`",".join(["a", "b"])`	`"a,b"`
`startswith(prefix)`	`"hello".startswith("he")`	`True`
`endswith(suffix)`	`"hello".endswith("lo")`	`True`
`find(sub)`	`"hello".find("ll")`	`2`
`count(sub)`	`"hello".count("l")`	`2`
`isdigit()`	`"123".isdigit()`	`True`
`isalpha()`	`"abc".isalpha()`	`True`
`isalnum()`	`"abc123".isalnum()`	`True`
`isspace()`	`" ".isspace()`	`True`

Escape Sequences¶

"\n"    # Newline
"\t"    # Tab
"\\"    # Backslash
"\""    # Double quote
"\'"    # Single quote
"\r"    # Carriage return
"\b"    # Backspace

String Operations¶

# Concatenation
s = "Hello" + " " + "World"  # "Hello World"

# Repetition
s = "ab" * 3  # "ababab"

# Membership
"ell" in "hello"  # True
"xyz" not in "hello"  # True

# Length
len("hello")  # 5

Useful Patterns¶

# Split and process
words = "apple,banana,cherry".split(",")
# ["apple", "banana", "cherry"]

# Join with separator
result = " - ".join(["a", "b", "c"])
# "a - b - c"

# Strip whitespace
user_input = input().strip()

# Case-insensitive comparison
if user_input.lower() == "yes":
    print("User said yes")

# Check if string contains substring
if "error" in message:
    print("Error found")

# Replace multiple occurrences
text = "foo bar foo".replace("foo", "baz")
# "baz bar baz"

# Format with multiple values
template = "Name: {}, Age: {}"
result = template.format("Alice", 30)

Common String Mistakes¶

Strings are immutable: s[0] = 'x' raises TypeError. Create a new string instead.
Indexing out of bounds: "hello"[10] raises IndexError. Use slicing instead: "hello"[10:] returns "".
Forgetting .strip() on input: input() includes the newline. Use input().strip().
Mixing string types: "hello" + 5 raises TypeError. Convert first: "hello" + str(5).
Forgetting .join() for lists: ", ".join(["a", "b"]) not ", " + ["a", "b"].
Case sensitivity: "Hello" != "hello". Use .lower() for case-insensitive comparison.