String Operations in Python

A string is a sequence of characters (letters, numbers, symbols, spaces) enclosed in quotes.

name = "Danny"
message = 'Hello World'

You can use:

• Single quotes ' '
• Double quotes " "
• Triple quotes ''' ''' or """ """ (for multi-line text)

Basic String Operations

1️⃣ Concatenation (Joining Strings)

Combining two or more strings using +.

first = "Hello"
second = "World"

result = first + " " + second
print(result)

Output:

Hello World

2️⃣ Repetition

Repeat a string using *.

word = "Hi "
print(word * 3)

Output:

Hi Hi Hi

3️⃣ Indexing (Accessing Characters)

Each character has a position (index).

text = "Python"
print(text[0])   # First character
print(text[-1])  # Last character

📊 Index Table

| Character | P | y | t | h | o | n |
|-----------|---|---|---|---|---|---|
| Index     | 0 | 1 | 2 | 3 | 4 | 5 |
| Negative  | -6|-5 |-4 |-3 |-2 |-1 |

4️⃣ Slicing (Getting Part of a String)

text = "Python Programming"

print(text[0:6])   # Python
print(text[7:18])  # Programming
print(text[:6])    # Python
print(text[7:])    # Programming

Useful String Functions (Methods)

Common String Methods

| Method | Description | Example |
|--------|------------|---------|
| lower() | Converts to lowercase | "PYTHON".lower() → python |
| upper() | Converts to uppercase | "python".upper() → PYTHON |
| title() | Capitalizes each word | "hello world".title() |
| capitalize() | Capitalizes first letter | "python".capitalize() |
| strip() | Removes spaces from both ends | " hi ".strip() |
| lstrip() | Removes left spaces | " hi".lstrip() |
| rstrip() | Removes right spaces | "hi ".rstrip() |

5️⃣ Replacing Text

text = "I like Java"
print(text.replace("Java", "Python"))

Output:

I like Python

6️⃣ Splitting Strings

Convert a string into a list.

sentence = "Python is fun"
print(sentence.split())

Output:

['Python', 'is', 'fun']

7️⃣ Joining Strings

words = ['Python', 'is', 'fun']
print(" ".join(words))

Output:

Python is fun

String Checking Methods

These return True or False.

| Method | Meaning | Example |
|--------|---------|---------|
| isalpha() | Only letters | "Python".isalpha() |
| isdigit() | Only numbers | "123".isdigit() |
| isalnum() | Letters & numbers | "Python3".isalnum() |
| islower() | All lowercase | "python".islower() |
| isupper() | All uppercase | "PYTHON".isupper() |
| startswith() | Begins with | "Hello".startswith("H") |
| endswith() | Ends with | "Hello".endswith("o") |

Finding Text in a String

text = "I love Python"

print(text.find("Python"))   # Returns position
print(text.count("o"))       # Counts occurrences

String Length

text = "Python"
print(len(text))

String Formatting (Very Important )

1. Using f-strings

name = "Danny"
age = 25

print(f"My name is {name} and I am {age} years old")

2. Using format()

print("My name is {} and I am {}".format(name, age))

Escape Characters

Used for special formatting.

| Escape | Meaning |
|--------|---------|
| \n | New line |
| \t | Tab |
| \\ | Backslash |
| \" | Double quote |
| \' | Single quote |

Example:

print("Hello\nWorld")

Multiline Strings

text = """This is
a multiline
string"""

Membership Operators

Check if a value exists in a string.

text = "Python"

print("P" in text)      # True
print("Java" not in text)  # True

Examples

Example 1: User Input Formatter

name = input("Enter your name: ").strip().title()
print(f"Welcome {name}")

Example 2: Email Checker

email = input("Enter email: ")

if "@" in email and "." in email:
    print("Valid email")
else:
    print("Invalid email")