--- id: python-string title: String in Python sidebar_label: String in Python #displays in sidebar sidebar_position: 7 tags: [ Python, Introduction of python, Python Syntax, Variables, Operators, Type Casting, String ] --- In Python, a **string** is a sequence of characters enclosed within **single (`'`)**, **double (`"`)**, or **triple quotes (`''' '''` or `""" """`)**. It is used to store and manipulate **textual data**. ```python str1 = 'Hello' str2 = "World" str3 = '''This is a multi-line string.''' ```` ## Creating Strings Strings can be created in several ways: ```python name = "Dhruba" message = 'Welcome to Python' multiline = """This is a multiline string.""" ``` ## String Indexing and Slicing **Indexing**: Access characters by position (starting at index 0). ```python text = "Python" print(text[0]) # P print(text[-1]) # n ``` **Slicing**: Extract a part of the string. ```python print(text[0:3]) # Pyt print(text[::2]) # Pto print(text[1:-1]) # ytho ``` ## String Methods | Method | Description | | ----------------- | ------------------------------------ | | `upper()` | Converts all characters to uppercase | | `lower()` | Converts all characters to lowercase | | `strip()` | Removes spaces from both ends | | `replace(a, b)` | Replaces `a` with `b` | | `startswith(val)` | Checks if string starts with `val` | | `endswith(val)` | Checks if string ends with `val` | | `find(val)` | Finds the first index of `val` | | `count(val)` | Counts occurrences of `val` | ```python msg = " Hello Python " print(msg.upper()) # HELLO PYTHON print(msg.strip()) # Hello Python print(msg.replace("Python", "JS")) # Hello JS ``` ## String Concatenation and Repetition **Concatenation** with `+`: ```python first = "Hello" second = "World" print(first + " " + second) # Hello World ``` **Repetition** with `*`: ```python print("Hi! " * 3) # Hi! Hi! Hi! ``` ## Using `in` and `not in` Operators Check for substring presence: ```python text = "Python is fun" print("fun" in text) # True print("Java" not in text) # True ``` ## String Formatting ### f-string (Python 3.6+) ```python name = "Dhruba" age = 22 print(f"My name is {name} and I am {age} years old.") ``` ### format() method ```python print("My name is {} and I am {} years old.".format(name, age)) ``` ### % operator ```python print("My name is %s and I am %d years old." % (name, age)) ``` --- ## Escape Sequences Escape characters add special formatting in strings: | Escape | Meaning | | ------ | ------------ | | `\n` | New line | | `\t` | Tab space | | `\\` | Backslash | | `\'` | Single quote | | `\"` | Double quote | ```python print("Hello\nWorld") # Line break print("Name:\tDhruba") # Tab ``` ## Multiline Strings Triple quotes allow multi-line text: ```python message = """This is line 1 This is line 2 This is line 3""" print(message) ``` ## Use Cases and Examples ### Greet user ```python name = input("Enter your name: ") print(f"Welcome, {name}!") ``` ### Count letters ```python text = "banana" print(text.count("a")) # 3 ``` ### Read file and process ```python with open("file.txt") as f: data = f.read() print(data.lower()) ``` ### Validate email domain ```python email = "[email protected]" if email.endswith("@example.com"): print("Valid domain") ``` ## Summary * Strings are **immutable** sequences of characters. * Support **indexing**, **slicing**, **concatenation**, and **repetition**. * Useful **methods** help in text processing. * Use **escape sequences** for formatting. * Use **f-strings** or `format()` for clean formatting.