String Manipulation.md

String Manipulation

Table of Contents

• Basic String Operations
• Common String Methods
• String Formatting
• Slicing and Indexing Strings
  • Indexing
  • Slicing
  • Step

---

Basic String Operations

• Concatenation: Joining multiple strings into a single string. In Python, the + operator is used for concatenation.

  first_name = "John"
  last_name = "Doe"
  full_name = first_name + " " + last_name  # "John Doe"

• Repetition: Creating a repeated sequence of a string by using the * operator.

  laugh = "ha"
  repeated_laugh = laugh * 3  # "hahaha"

---

Common String Methods

1. find(): Returns the index of the first occurrence of a substring. If the substring is not found, it returns -1.

text = "Hello, world!"
index = text.find("world")  # 7

2. replace(): Replaces occurrences of a substring within a string with another substring.

text = "I like apples"
new_text = text.replace("apples", "oranges")  # "I like oranges"

3. split(): Splits a string into a list of substrings based on a specified delimiter (default is whitespace).

sentence = "Hello world"
words = sentence.split()  # ["Hello", "world"]

4. join(): Combines elements of a list or iterable into a single string, with a specified separator.

words = ["Hello", "world"]
sentence = " ".join(words)  # "Hello world"

5. upper() upper() lower(): Converts a string to uppercase or lowercase.

text = "Hello"
text_upper = text.upper()  # "HELLO"
text_lower = text.lower()  # "hello"

6. strip(): Removes leading and trailing whitespace or specified characters.

text = "   Hello   "
stripped_text = text.strip()  # "Hello"

---

String Formatting

• f-strings (formatted string literals): A concise way to embed expressions inside string literals, available in Python 3.6 and later. Place variables or expressions within {} brackets prefixed by f.

  name = "Alice"
  age = 25
  info = f"{name} is {age} years old."  # "Alice is 25 years old."

• format() method: Allows placeholders in a string to be replaced by variables, using {} brackets.

  name = "Alice"
  age = 25
  info = "{} is {} years old.".format(name, age)  # "Alice is 25 years old."

• % operator: Another way to format strings, especially common in older Python code.

  name = "Alice"
  age = 25
  info = "%s is %d years old." % (name, age)  # "Alice is 25 years old."

---

Slicing and Indexing Strings

• Indexing

Accessing individual characters in a string by their index, starting from 0.

text = "Hello"
first_char = text[0]  # "H"
last_char = text[-1]  # "o"

• Slicing

Extracting a substring by specifying a range of indices. The syntax text[start:end] returns characters from the start index up to, but not including, the end index.

text = "Hello, world!"
slice1 = text[0:5]  # "Hello"
slice2 = text[7:]  # "world!"
slice3 = text[:5]  # "Hello"

• Step

An optional third parameter for slices to specify the step value. This is useful for reversing a string.

text = "Hello, world!"
reversed_text = text[::-1]  # "!dlrow ,olleH"