String Manipulation in Python

String Manipulation in Python

Strings in Python are sequences of characters enclosed in single, double, or triple quotes. Strings are immutable, but Python provides many ways to manipulate them.

Creating strings:
Example:
str1 = "Hello"
str2 = 'Python'
str3 = """This is a
multi-line string"""

Accessing characters:
Use indexing to access individual characters. Indexing starts at 0.
Example:
print(str1[0]) # H
print(str1[-1]) # o (last character)

Slicing strings:
Extract a part of a string using slicing: string[start:end]
Example:
print(str1[0:3]) # Hel
print(str1[:3]) # Hel
print(str1[2:]) # llo
print(str1[::2]) # Hlo (every second character)

String concatenation:
Use + to join strings.
Example:
greeting = "Hello " + "World"
print(greeting) # Hello World

String repetition:
Use * to repeat strings.
Example:
print("Hi! " * 3) # Hi! Hi! Hi!

String methods:

• lower(): converts to lowercase

• upper(): converts to uppercase

• title(): capitalizes first letter of each word

• strip(): removes leading and trailing whitespace

• replace(old, new): replaces substring

• split(): splits string into a list

• join(): joins a list of strings into a single string
  Example:
  text = " Python Programming "
  print(text.lower()) # python programming
  print(text.upper()) # PYTHON PROGRAMMING
  print(text.strip()) # Python Programming
  print(text.replace("Python", "Java")) # Java Programming
  words = text.split()
  print(words) # ['Python', 'Programming']
  print("-".join(words)) # Python-Programming

Checking content:

• startswith() / endswith(): checks start or end

• isalpha(): all letters

• isdigit(): all digits

• isalnum(): letters or digits
  Example:
  s = "Python3"
  print(s.isalpha()) # False
  print(s.isalnum()) # True
  print(s.startswith("Py")) # True

String formatting:

• f-strings:
  name = "Alice"
  age = 25
  print(f"My name is {name} and I am {age} years old")

• format() method:
  print("My name is {} and I am {} years old".format(name, age))

• % formatting:
  print("My name is %s and I am %d years old" % (name, age))

Multiline strings:
Use triple quotes for multiple lines.
Example:
msg = """This is
a multiline
string"""
print(msg)

Escape characters:

• \n → new line

• \t → tab

• \\ → backslash

• \' → single quote

• \" → double quote