🎯 Lesson Objective
To understand how to work with text data in Python, perform string operations, and use built-in string methods for manipulation and analysis.
🧠 1. What Is a String?
A string is a sequence of characters enclosed in single quotes (”), double quotes (“”), or triple quotes (”’ ”’).
✅ Example:
name = "Sameer"
greeting = 'Hello!'
message = '''Welcome to Python programming.'''
⚙️ 2. Accessing String Characters
Strings are indexed, meaning each character has a position (starting from 0).
text = "Python"
print(text[0]) # First character
print(text[5]) # Last character
Output:
P
n
🔄 3. String Slicing
You can extract parts of a string using slicing.
word = "Programming"
print(word[0:6]) # Output: Progra
print(word[3:]) # Output: gramming
print(word[:5]) # Output: Progr
print(word[-3:]) # Output: ing
🧩 4. String Concatenation and Repetition
You can join strings using + and repeat using *.
a = "Hello"
b = "Python"
print(a + " " + b) # Concatenation
print(a * 3) # Repetition
Output:
Hello Python
HelloHelloHello
🔢 5. String Length
Find the number of characters using len().
text = "Python"
print(len(text))
Output:
6
✂️ 6. Checking for Substrings
You can check if a substring exists using the in or not in operator.
text = "Learning Python"
print("Python" in text)
print("Java" not in text)
Output:
True
True
🧰 7. Common String Methods
| Method | Description | Example |
|---|---|---|
upper() | Converts all characters to uppercase | "hello".upper() → HELLO |
lower() | Converts all characters to lowercase | "HELLO".lower() → hello |
title() | Capitalizes first letter of each word | "hello world".title() → Hello World |
strip() | Removes spaces from start and end | " hello ".strip() → hello |
replace() | Replaces substring | "I love Java".replace("Java", "Python") → I love Python |
split() | Splits string into list | "a,b,c".split(",") → ['a', 'b', 'c'] |
join() | Joins list into a string | "-".join(['a','b','c']) → a-b-c |
find() | Returns index of substring | "python".find("th") → 2 |
count() | Counts occurrences | "apple".count("p") → 2 |
startswith() / endswith() | Checks prefix/suffix | "Python".startswith("Py") → True |
🔤 8. Escape Characters
Used to include special characters inside strings.
| Escape Code | Meaning | Example |
|---|---|---|
\' | Single quote | 'It\'s fun' |
\" | Double quote | "He said \"Hi\"" |
\\ | Backslash | "C:\\Users" |
\n | New line | "Hello\nWorld" |
\t | Tab space | "Hello\tWorld" |
✅ Example:
print("Name:\tSameer\nCity:\tWarangal")
Output:
Name: Sameer
City: Warangal
🧮 9. String Formatting
You can use f-strings or format() for neat output.
name = "Sameer"
age = 25
print(f"My name is {name} and I am {age} years old.")
Output:
My name is Sameer and I am 25 years old.
🌍 10. Real-Life Example: Text Analyzer
text = input("Enter a sentence: ")
print("Total characters:", len(text))
print("Uppercase:", text.upper())
print("Number of spaces:", text.count(" "))
print("Reversed:", text[::-1])
Output (for input “Python is fun”):
Total characters: 13
Uppercase: PYTHON IS FUN
Number of spaces: 2
Reversed: nuf si nohtyP
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