Learn Python from Scratch 2023: Module 3

Module 3: Data Structures

3.1 Introduction to Data Structures:

Data structures are containers that hold data in an organized and efficient manner. In Python, there are four built-in data structures: lists, tuples, sets, and dictionaries.

3.2 Lists:

Lists are a collection of values that are ordered and changeable. They are defined by enclosing a comma-separated sequence of values in square brackets []. Here’s an example:

fruits = ["apple", "banana", "cherry"]

To access a specific element in a list, you can use indexing. Indexing starts at 0 in Python, so to access the first element of the fruits list, you would use the index 0:

print(fruits[0]) # Output: "apple"

You can also use negative indexing to access elements from the end of the list:

print(fruits[-1]) # Output: "cherry"

Lists are mutable, which means you can change their values. For example, you can add an element to the end of a list using the append() method:

fruits.append("orange")
print(fruits) # Output: ["apple", "banana", "cherry", "orange"]

3.3 Tuples:

Tuples are similar to lists, but they are immutable, which means you cannot change their values. They are defined by enclosing a comma-separated sequence of values in parentheses (). Here’s an example:

fruits = ("apple", "banana", "cherry")

You can access elements in a tuple using indexing, just like with lists:

print(fruits[0]) # Output: "apple"

However, you cannot change the values of a tuple:

fruits[0] = "orange" # This will result in an error

3.4: Sets

Sets are a collection of unique values that are unordered and unindexed. They are defined by enclosing a comma-separated sequence of values in curly braces {}. Here’s an example:

fruits = {"apple", "banana", "cherry"}

You cannot access elements in a set using indexing, but you can check if a value is in a set using the “in” keyword:

print("banana" in fruits) # Output: True

You can add elements to a set using the add() method:

fruits.add("orange")
print(fruits) # Output: {"apple", "banana", "cherry", "orange"}

Submodule 3.5

Dictionaries Dictionaries are a collection of key-value pairs that are unordered and changeable. They are defined by enclosing a comma-separated sequence of key-value pairs in curly braces {}, where each key-value pair is separated by a colon :. Here’s an example:

person = {"name": "John", "age": 30, "city": "New York"}

You can access the value of a specific key in a dictionary using indexing:

print(person["name"]) # Output: "John"

You can also change the value of a key:

person["age"] = 40
print(person) # Output: {"name": "John", "age": 40, "city": "New York"}

To add a new key-value pair to a dictionary, you can simply assign a value to a new key:

person["gender"] = "Male"
print(person) # Output: {"name