3.2 Strings

Data Abstraction: Strings

Introduction to Strings

In programming, a string is a sequence of characters. Strings can include letters, numbers, symbols, and whitespace. Strings are used to represent text in a program.

Key Characteristics of Strings

• Strings are enclosed in quotes (single or double).
• They are immutable, meaning once created, they cannot be changed.
• Strings can be indexed and sliced.

Definition of a String

A string is a data type used in programming to represent text. It is a sequence of characters, which can include letters, digits, punctuation marks, and spaces.

Example:

my_string = "Hello, World!"


## String Operations

Strings support various operations. Here are some common ones:

### 1. String Length
You can find the length of a string using the `len()` function.

### Example:
```python
length = len(my_string)
print(length)  # Output: 13


```python
```python
# String Length
length = len(my_string)
print(f"Length of the string: {length}")  # Output: Length of the string: 13

2. String Indexing

Strings can be accessed using indices. The first character has an index of 0.

Example:

first_character = my_string[0]
print(first_character)  # Output: H



```python
```python
# String Indexing
first_character = my_string[0]
print(f"First character of the string: {first_character}")  # Output: H

3. String Slicing

You can extract a portion of a string using slicing.

Example:

substring = my_string[0:5]
print(substring)  # Output: Hello


```python
```python
# String Slicing
substring = my_string[0:5]
print(f"Substring: {substring}")  # Output: Hello

4. String Methods

Strings come with various built-in methods. Here are a few useful ones:

• lower(): Converts a string to lowercase.
• upper(): Converts a string to uppercase.
• replace(): Replaces a substring with another substring.

Example:

lower_string = my_string.lower()
print(lower_string)  # Output: hello, world!



```python
```python
# String Methods
lower_string = my_string.lower()
upper_string = my_string.upper()
replaced_string = my_string.replace("World", "Python")

print(f"Lowercase: {lower_string}")  # Output: hello, world!
print(f"Uppercase: {upper_string}")  # Output: HELLO, WORLD!
print(f"Replaced String: {replaced_string}")  # Output: Hello, Python!

Conclusion

Strings are fundamental in programming, especially for handling text. Understanding how to manipulate strings is crucial for any programmer. In this lesson, we covered the basics of strings, including their definition, length, indexing, slicing, and some common string methods.