Python Basics — String Creation & Indexing

String Creation & Indexing

Strings are sequences of characters. Python provides multiple ways to create them and powerful tools to access individual characters.

String Creation Methods

Single and Double Quotes

name = 'Alice'
greeting = "Hello, World!"

# Both are identical
print(type(name))     # <class 'str'>
print(type(greeting)) # <class 'str'>

Use single quotes when the string contains double quotes, and vice versa:

quote = 'She said "hello"'
html = "<p class='main'>Text</p>"

Triple Quotes (Multi-Line Strings)

message = """This is a
multi-line
string."""

print(message)

Output:

This is a
multi-line
string.

Triple quotes preserve line breaks and are also used for docstrings.

Empty Strings

empty = ""
also_empty = str()

print(len(empty))       # 0
print(bool(empty))      # False (empty string is falsy)
print(bool("hello"))    # True (non-empty string is truthy)

Positive and Negative Indexing

Every character in a string has an index position. Python supports both positive (left-to-right) and negative (right-to-left) indexing:

String:  P   y   t   h   o   n
Index:   0   1   2   3   4   5
Neg:    -6  -5  -4  -3  -2  -1

word = "Python"

# Positive indexing (starts at 0)
print(word[0])   # P
print(word[1])   # y
print(word[5])   # n

# Negative indexing (starts at -1)
print(word[-1])  # n
print(word[-2])  # o
print(word[-6])  # P

IndexError

Accessing an index that doesn’t exist raises an error:

word = "Python"
# print(word[10])  # IndexError: string index out of range

String Length with len()

message = "Hello, World!"
print(len(message))   # 13

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

Spaces, punctuation, and special characters all count:

print(len("a b"))     # 3 (includes the space)
print(len("\t\n"))     # 2 (tab + newline)

Iterating Over Strings

word = "Hello"

for char in word:
    print(char, end=" ")

Output:

H e l l o

With enumerate():

word = "Hello"

for index, char in enumerate(word):
    print(f"Index {index}: '{char}'")

Output:

Index 0: 'H'
Index 1: 'e'
Index 2: 'l'
Index 3: 'l'
Index 4: 'o'

Escape Characters

Escape	Description	Example	Output
\n	Newline	"a\nb"	a(newline)b
\t	Tab	"a\tb"	a(tab)b
\\	Backslash	"a\\b"	a\b
\'	Single quote	'it\'s'	it’s
\"	Double quote	"say \"hi\""	say “hi”

print("First\nSecond")
print("Column1\tColumn2")
print("Path: C:\\Users\\docs")

Output:

First
Second
Column1	Column2
Path: C:\Users\docs

Raw Strings

Prefix with r to ignore escape characters:

# Normal string
print("C:\new\folder")    # C: (newline) ew (tab) older

# Raw string
print(r"C:\new\folder")   # C:\new\folder

Raw strings are essential for:

• Windows file paths
• Regular expressions
• Any string with lots of backslashes

String Immutability

Strings cannot be changed in place:

word = "Python"
# word[0] = "J"  # TypeError: 'str' object does not support item assignment

To “modify” a string, create a new one:

word = "Python"
new_word = "J" + word[1:]
print(new_word)  # Jython

String Concatenation and Repetition

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

# Repetition with *
line = "-" * 30
print(line)  # ------------------------------

# Implicit concatenation (adjacent string literals)
message = "Hello " "World"
print(message)  # Hello World

Membership Testing

message = "Hello, World!"

print("Hello" in message)     # True
print("hello" in message)     # False (case-sensitive)
print("xyz" not in message)   # True

Summary

• Create strings with 'single', "double", or """triple""" quotes
• Access characters with positive ([0]) or negative ([-1]) indexing
• Use len() to get string length
• Escape characters: \n, \t, \\, \', \"
• Raw strings (r"...") ignore escape sequences
• Strings are immutable — operations create new strings
• Use in to check if a substring exists

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Next up: String Slicing →