Introduction to Strings as Data Structures

Strings in Python are sequences of characters. They can be treated as data structures because they support indexing, slicing, and various methods for manipulation.

In this lesson, you’ll learn how to work with strings and use their powerful methods.

Creating Strings

Strings are created by enclosing characters in single, double, or triple quotes:

# Creating a string
text = "Hello, World!"
print(text)

String Indexing and Slicing

You can access individual characters or substrings using indexing and slicing:

# String indexing and slicing
text = "Hello, World!"
print(text[0])  # Outputs: H
print(text[0:5])  # Outputs: Hello

String Concatenation and Repetition

You can concatenate strings using the + operator and repeat them using the * operator:

# String concatenation and repetition
greeting = "Hello" + ", World!"
print(greeting)  # Outputs: Hello, World!
print("Hi! " * 3)  # Outputs: Hi! Hi! Hi!

String Methods: Basic Operations

Python provides many methods for string manipulation: 

• lower(): Converts all characters to lowercase. 
• upper(): Converts all characters to uppercase. 
• strip(): Removes whitespace from the beginning and end.

# String methods
text = "  Hello, World!  "
print(text.strip())  # Outputs: Hello, World!

Finding Substrings

You can search for substrings using methods like find() and in:

# Finding substrings
text = "Hello, World!"
print(text.find("World"))  # Outputs: 7
print("World" in text)  # Outputs: True

Splitting and Joining Strings

You can split a string into a list of words or join a list of words into a single string:

# Splitting and joining strings
text = "apple,banana,cherry"
words = text.split(",")
print(words)  # Outputs: ['apple', 'banana', 'cherry']
print(",".join(words))  # Outputs: apple,banana,cherry

Common Mistakes with Strings

Here are some mistakes to avoid:

• Trying to modify a string (strings are immutable).
• Forgetting that string indexing starts at 0.
• Using incorrect syntax for string methods.

What Did We Learn?

In this lesson, you learned:

• How to create and manipulate strings in Python.
• String indexing, slicing, and methods for manipulation.
• How to split and join strings for data processing.

Great job! Let’s move to the next topic.