String Data and Methods

2. Escape Character and Special Characters

2.1 Escape Character
1. text = "Name:\tRabindra" print(text)Output: Name: Rabindra 😕 Why did Python show extra space instead of printing \t? This happened because \t has a special meaning in Python strings. \t is an escape sequence that creates a tab space. The backslash \ is called an escape character. It is used to give special meaning to the character that comes after it. Few Special Characters:\n creates a new line. \t creates a tab space. \\ prints a backslash.

2.2 Examples
1. str_1 = 'Hello, I\'m learning Python!' print(str_1) # ➜ Hello, I'm learning Python! str_2 = "Name:\tRabindra" print(str_2) # ➜ Name: Rabindra str_3 = "This is a backslash: \\" print(str_3) # ➜ This is a backslash: \ str_4 = "I have a pen.\nIt is good." print(str_4)Output: I have a pen. It is good.
2.3 Printing Literal Escape Sequences
1. If we want to print \n, \t as normal text instead of creating a new line, we need to escape the backslash. Example: text = "This is newline symbol: \\n" print(text) # ➜ This is newline symbol: \n text = "\\n and \\t are escape sequences." print(text) # ➜ \n and \t are escape sequences.

3. Indexing and Slicing

3.1 Indexing [ ]
1. Indexing is used to access a single character from a string. Each character in a string can be accessed using positive or negative index. Example: text = "Python" Index positions: P y t h o n 0 1 2 3 4 5 -6 -5 -4 -3 -2 -1 print(text[0]) # ➜ P print(text[-6]) # ➜ P print(text[5]) # ➜ n print(text[-1]) # ➜ n

3.2 Indexing Examples
1. str_1 = "Python is fun"print(str_1[0]) # ➜ P print(str_1[4]) # ➜ o print(str_1[-1]) # ➜ n print(str_1[7]) # ➜ i
3.3 Slicing [start:stop:step]
1. Slicing is used to extract a part of a string. Syntax: variable[start:stop:step] start ➜ Starting index stop ➜ Stopping index, but not included step ➜ Number of characters to skip 📌 Start is included. 📌 Stop is not included. 📌 Step is optional. 📌 If start is not given, slicing begins from the start. 📌 If stop is not given, slicing continues till the end.

3.4 Slicing Examples
1. str_1 = "Python is fun"print(str_1[0:6]) # ➜ Python print(str_1[0:6:2]) # ➜ Pto print(str_1[:3]) # ➜ Pyt print(str_1[10:]) # ➜ fun print(str_1[::-1]) # ➜ nuf si nohtyP
3.5 Strings are Immutable
1. Strings are immutable. This means once a string is created, it cannot be changed directly in-place. If we apply a string method, Python creates a new string instead of changing the original string. Example: text = "hello" text[2] = "P" ⚠️ This line gives an error because individual characters in a string cannot be changed directly.

4. Basic String Operations

4.1 Concatenation (+)
1. Concatenation means combining two or more strings. The + operator is used for string concatenation. Example: str_1 = "Hello," str_2 = "World!"greeting = str_1 + " " + str_2 print(greeting) # ➜ Hello, World! print("Python " + "is " + "fun!") # ➜ Python is fun!

4.2 Repetition (*)
1. Repetition means repeating a string multiple times. The * operator is used for string repetition. Example: str_1 = "Hello "repeated_str = str_1 * 3 print(repeated_str) # ➜ Hello Hello Hello print("abc" * 5) # ➜ abcabcabcabcabc
4.3 Length len()
1. len() is used to count the number of characters in a string. Example: str_1 = "Hello, World!"print(len(str_1)) # ➜ 13 print(len("Python")) # ➜ 6 print(len("abc")) # ➜ 3 📌 Spaces, commas, and symbols are also counted as characters.

5. String Methods

5.1 What are String Methods?
1. String methods are built-in operations used to work with text. They help us: 🔠 Change case ✅ Check text 🧹 Clean text ✂️ Split text 🔗 Join text 🔍 Search text 🔁 Replace text 🔢 Count text 📌 Since strings are immutable, string methods usually return a new string instead of changing the original string.

5.2 Case Methods 🔠
1. Case methods are used to check or change uppercase/lowercase letters. Common Methods: isupper() ➜ Checks if string is uppercase islower() ➜ Checks if string is lowercase istitle() ➜ Checks if each word starts with uppercase and remaining letters are lowercase upper() ➜ Converts to uppercase lower() ➜ Converts to lowercase title() ➜ Converts to title case swapcase() ➜ Swaps uppercase and lowercase Examples: str_1 = "Hello, World!"print(str_1.isupper()) # ➜ False (returns True only when all characters are in uppercase) print(str_1.islower()) # ➜ False (returns True only when all characters are in lowercase) print("PYTHON".isupper()) # ➜ True print("python".islower()) # ➜ True print("Hello".istitle()) # ➜ True print(str_1.upper()) # ➜ HELLO, WORLD! print(str_1.lower()) # ➜ hello, world! print(str_1.title()) # ➜ Hello, World! print(str_1.swapcase()) # ➜ hELLO, wORLD!
5.3 Data Checking Methods ✅
1. Data checking methods check what kind of characters a string contains. Common Methods: isalpha() ➜ Checks if all characters are alphabets isdigit() ➜ Checks if all characters are digits isalnum() ➜ Checks if all characters are alphabets or numbers isspace() ➜ Checks if all characters are whitespace startswith() ➜ Checks if string starts with given text endswith() ➜ Checks if string ends with given text Examples: str_1 = "Hello"print(str_1.isalpha()) # ➜ True print(str_1.isdigit()) # ➜ False print("123".isdigit()) # ➜ True print("abc123".isalnum()) # ➜ True print(" ".isspace()) # ➜ True print("Hello123".isalpha()) # ➜ False file_name = "2026-03-01.csv"print(file_name.startswith("2026")) # ➜ True print(file_name.endswith(".csv")) # ➜ True print(file_name.endswith(".pdf")) # ➜ False print(file_name.startswith("03")) # ➜ False
5.4 Cleanup Methods 🧹
1. Cleanup methods remove unnecessary characters from a string. Common Methods: strip() ➜ Removes characters from both left and right side lstrip() ➜ Removes characters from left side only rstrip() ➜ Removes characters from right side only Examples: str_1 = " Hello, World! "clean_str = str_1.strip() print(clean_str) # ➜ "Hello, World!" print("###Data # Fun###".strip("#")) # ➜ "Data # Fun" print("###Data###".lstrip("#")) # ➜ "Data###" print("###Data###".rstrip("#")) # ➜ "###Data"
5.5 Split and Join Methods ✂️ 🔗
1. split() ➜ Breaks a string into a list based on split character provided. join() ➜ Joins a list of strings into one string. split() Examples: str_1 = "Hello, World!" print(str_1.split()) # ➜ ["Hello,", "World!"] date_separated = "2026-03-01.csv".split("-") print(date_separated) # ➜ ["2026", "03", "01.csv"] print("apple,banana,orange".split(",")) # ➜ ["apple", "banana", "orange"] join() Examples: str_list = ["Hello", "World"] print(" ".join(str_list)) # ➜ "Hello World" print("-".join(["2026", "03", "01"])) # ➜ "2026-03-01" print(",".join(["apple", "banana", "orange"])) # ➜ "apple,banana,orange" print(".".join("apple")) # ➜ "a.p.p.l.e"
5.6 Search, Replace, and Count Methods 🔍 🔁 🔢
1. These methods are used to find, replace, or count text inside a string. Common Methods: find() ➜ Finds index of text, returns -1 if not found index() ➜ Finds index of text, gives error if not found replace() ➜ Replaces text count() ➜ Counts text occurrence find() and index() Examples: str_1 = "Hello, World!"print(str_1.find("o")) # ➜ 4 (As o occurs first at index 4) print(str_1.index("o")) # ➜ 4 print(str_1.find("z")) # ➜ -1 print(str_1.index("z")) # ➜ ValueError ⚠️ This line gives an error because "z" is not found. 📌 find() returns -1 if text is not found. 📌 index() raises ValueError if text is not found. replace() Examples: str_1 = "Hello, World!" new_str = str_1.replace("World", "Python") print(new_str) # ➜ "Hello, Python!" print("2026-03-01.csv".replace("-", "/")) # ➜ "2026/03/01.csv" print("apple,banana,orange".replace(",", ";")) # ➜ "apple;banana;orange" count() Examples: str_1 = "Hello, World!" count_of_o = str_1.count("o") print(count_of_o) # ➜ 2 print("banana,apple".count("banana")) # ➜ 1 print("2026-03-01.csv".count("-")) # ➜ 2 print("test_exercise.py".count(".pdf")) # ➜ 0