day-07

Lists, Tuples, and Dictionaries

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Introduction to Data Structures

• Data structures in Python are essential tools for storing, organizing, and managing data efficiently. They offer diverse ways to store and retrieve data, tailored to specific needs. These structures enable data manipulation, efficient searching, and complex data modeling, ensuring optimal performance and maintainability in Python programs.

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Lists

In Python, a list is an ordered collection of elements. Lists are one of the most commonly used data structures and are versatile, allowing you to store a sequence of values, such as numbers, strings, or even other lists. Lists are mutable, meaning you can change their content (add, remove, or modify elements) after they are created. Lists are defined using square brackets [] and elements within the list are separated by commas.

Creating a List:

To create a list in Python, enclose the elements within square brackets.

my_list = [1, 2, 3, 4, 5]

Accessing Elements:

You can access elements of a list by their index. Python uses zero-based indexing, so the first element is at index 0, the second at 1, and so on.

first_element = my_list[0]  # Access the first element

Modifying Lists:

Lists are mutable, so you can add, remove, or change elements.

• Adding Elements

  • Append an element to the end of the list:

    my_list.append(6)

  • Insert an element at a specific index:

    my_list.insert(2, 7)  # Inserts 7 at index 2

• Removing Elements:

  • Remove the last element:

    my_list.pop()

  • Remove a specific element by value:

    my_list.remove(4)  # Removes the first occurrence of 4

• Changing Elements:

  • Modify an element by assignment:

    my_list[1] = 10  # Changes the second element to 10

    
    

List Slicing:

You can create sublists by slicing a list. This allows you to extract a portion of the list.

sub_list = my_list[1:4]  # Creates a sublist with elements from index 1 to 3

List Functions and Methods:

Python provides various functions and methods for list manipulation. For instance, you can sort a list, find its length, and concatenate two lists using the sorted(), len(), and + functions, respectively.

sorted_list = sorted(my_list)
list_length = len(my_list)
concatenated_list = my_list + [8, 9]

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Tuples

In Python, a tuple is an ordered collection of elements, much like a list. However, tuples are distinct from lists in one significant way: they are immutable. This means that once you create a tuple, you cannot change its content. Tuples are defined using parentheses () and elements within the tuple are separated by commas. Tuples are often used to group related data that should not change.

Creating a Tuple:

To create a tuple in Python, enclose the elements within parentheses.

my_tuple = (1, 2, 3, "apple", "banana")

Accessing Elements:

You can access elements of a tuple using zero-based indexing, similar to lists.

first_element = my_tuple[0]  # Access the first element

Tuples are Immutable:

Unlike lists, you cannot modify the elements of a tuple. Once a tuple is created, it cannot be changed, which means you can't add, remove, or change elements within it.

my_tuple[1] = 10  # This will raise a TypeError because tuples are immutable.

Tuple Packing and Unpacking:

Tuples are often used for packing and unpacking values. For example, you can create a tuple with multiple elements and then assign those elements to individual variables.

person = ("Alice", 30, "New York")
name, age, city = person  # Unpack the tuple into variables

Tuple Functions and Methods:

Tuples have several built-in functions and methods for various operations, such as finding the length and counting occurrences of an element.

tuple_length = len(my_tuple)
count_apple = my_tuple.count("apple")

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Dictionaries

In Python, a dictionary is a data structure used for storing and organizing data in the form of key-value pairs. Each key in a dictionary is associated with a value, creating a mapping between keys and their corresponding data. Dictionaries are flexible and allow you to efficiently retrieve, update, and manage data based on specific keys.

Creating a Dictionary:

To create a dictionary in Python, enclose key-value pairs within curly braces {}. Each pair consists of a key followed by a colon : and its corresponding value.

my_dict = {"name": "Alice", "age": 30, "city": "New York"}

Accessing Values:

You can access the values in a dictionary using the associated keys.

name = my_dict["name"]  # Access the value associated with the "name" key

• It's important to note that dictionary keys are case-sensitive.

Modifying Dictionaries:

Dictionaries are mutable, so you can add, change, or remove key-value pairs.

• Adding a Key-Value Pair:

  To add a new key-value pair, simply assign a value to a new key.

  my_dict["gender"] = "Female"  # Adds a new key-value pair

• Changing a Value:

  You can change the value associated with an existing key.

  my_dict["age"] = 31  # Updates the value associated with the "age" key

• Removing a Key-Value Pair:

  To remove a key-value pair, use the del statement.

  del my_dict["city"]  # Removes the key-value pair with the key "city"

Dictionary Methods:

Python provides a variety of methods to perform operations on dictionaries. For example, you can retrieve all keys, values, or items (key-value pairs) from a dictionary using methods like keys(), values(), and items().

keys_list = my_dict.keys()      # Returns a list of keys
values_list = my_dict.values()  # Returns a list of values
items_list = my_dict.items()    # Returns a list of key-value pairs

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Additional Resource:

• Lists, Tuples, and Dictionaries

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MINI PROJECT!!!

This will be the first requirement in the CodeQuest: 30 Days of Backend.

Create a basic shopping list program in Python. This program should allow users to add items to a shopping list, view the list, and remove items as needed.

Output:

Options:
1. Add item to the shopping list
2. View shopping list
3. Remove item from the shopping list
4. Quit
Enter the number of your choice: 1
Enter the item you want to add: Apples
Apples has been added to your shopping list.

Options:
1. Add item to the shopping list
2. View shopping list
3. Remove item from the shopping list
4. Quit
Enter the number of your choice: 1
Enter the item you want to add: Milk
Milk has been added to your shopping list.

Options:
1. Add item to the shopping list
2. View shopping list
3. Remove item from the shopping list
4. Quit
Enter the number of your choice: 2
Your shopping list:
Apples
Milk

Options:
1. Add item to the shopping list
2. View shopping list
3. Remove item from the shopping list
4. Quit
Enter the number of your choice: 3
Enter the item you want to remove: Apples
Apples has been removed from your shopping list.

Options:
1. Add item to the shopping list
2. View shopping list
3. Remove item from the shopping list
4. Quit
Enter the number of your choice: 2
Your shopping list:
Milk

Options:
1. Add item to the shopping list
2. View shopping list
3. Remove item from the shopping list
4. Quit
Enter the number of your choice: 4
Goodbye!