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Python Data Structures
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Python Data Structures

Python Data Structures

1. Mastering Python Lists
Creating Lists in Python: Declaring and Initializing ListsList Indexing in Python: Accessing Elements EfficientlyWorking with Nested Lists in PythonPython List Length: Measuring and Managing List SizeModifying Lists in Python: Updating and Changing ElementsUsing the append() Method: Adding Elements to ListsUsing the insert() Method: Placing Elements at Specific PositionsDeleting Elements in Python Lists: Removing Items SafelyUsing the remove() Method: Deleting Specific Elements from Lists
2. Mastering Python Dictionaries
Creating a Dictionary in Python: Storing Key-Value PairsAccessing Dictionary ValuesAccessing Dictionary KeysAdding Items to a Dictionary: Updating Key-Value PairsUsing the del Keyword: Removing Dictionary EntriesUsing the pop() Method: Deleting Elements with Return ValuesUsing the popitem() Method: Removing the Last Inserted ItemUsing the clear() Method: Emptying a Dictionary Completely
3. Mastering Python Tuples
Creating a Tuple in Python: Defining Immutable Data StructuresAccessing Elements in a Tuple: Indexing TechniqueConcatenating Tuples in Python: Merging Immutable SequencesDeleting Tuples in Python: Removing References to TuplesUpdating Tuples in PythonAdding Items to a Tuple: Alternative Approaches Using ListsCounting Elements in a Tuple: Using the count() MethodFinding Elements in a Tuple: Using the index() Method for Lookup
4. Mastering Python Sets
Creating a Set in Python: Defining Unordered CollectionsUsing the add() Method: Adding Single Elements to a SetUsing the update() Method: Merging Multiple Elements into a SetAccessing Elements in a Set: Iteration and Membership TestingUsing the remove() and discard() MethodsUsing the clear() Method: Removing All Elements from a Set

book
Modifying Lists in Python: Updating and Changing Elements

In Python, lists are mutable, which means that after a list is created, its contents can be modified, added, or removed. Because of this mutability, lists have much flexibility for working with lists and are, therefore, a very powerful tool for managing dynamic data.

What Does "Mutable" Mean?

Mutable means that the data structure can be updated without creating a new object. For example, you could change the value of an existing item, replace several elements, or even remove and insert new ones directly into the same list.

Imagine you have a list of cities you plan to visit, but plans change. You can update or replace items in the list easily:


              
123456789

            
cities = ["Paris", "Tokyo", "New York", "Berlin", "Sydney"]

# Replacing the fourth city
cities[2] = "Rome"
print(cities)  # Output: ['Paris', 'Tokyo', 'Rome', 'Berlin', 'Sydney']

# Replacing the last two cities with new ones
cities[-2:] = ["Dubai", "Cape Town"]
print(cities)  # Output: ['Paris', 'Tokyo', 'Rome', 'Dubai', 'Cape Town']
copy

In this example:

  1. We replaced the city "New York" at index 3 with "Rome";
  2. Using negative indexing, we replaced the last two cities ("Rome" and "Sydney") with "Dubai" and "Cape Town".

You can also make multiple changes in one step:


              
123456

            
cities = ["Paris", "Tokyo", "New York", "Berlin", "Sydney"]

# Replacing multiple cities in the middle
cities[1:3] = ["Seoul", "Bangkok", "Mumbai"]

print(cities)  # Output: ['Paris', 'Seoul', 'Bangkok', 'Mumbai', 'Berlin', 'Sydney']
copy

Here, we replaced "Tokyo" and "New York" with three cities: "Seoul", "Bangkok", and "Mumbai". This demonstrates how flexible list mutability can be for managing your data.

Uppgift

Swipe to start coding

You have a travel_wishlist list.

  • Update the estimated cost of all cities to include a discount.
  • Apply a 20% reduction to the cost (the third element in the nested list).
  • Use indexing to update the elements.

Lösning

Switch to desktopByt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan
Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 5
toggle bottom row

book
Modifying Lists in Python: Updating and Changing Elements

In Python, lists are mutable, which means that after a list is created, its contents can be modified, added, or removed. Because of this mutability, lists have much flexibility for working with lists and are, therefore, a very powerful tool for managing dynamic data.

What Does "Mutable" Mean?

Mutable means that the data structure can be updated without creating a new object. For example, you could change the value of an existing item, replace several elements, or even remove and insert new ones directly into the same list.

Imagine you have a list of cities you plan to visit, but plans change. You can update or replace items in the list easily:


              
123456789

            
cities = ["Paris", "Tokyo", "New York", "Berlin", "Sydney"]

# Replacing the fourth city
cities[2] = "Rome"
print(cities)  # Output: ['Paris', 'Tokyo', 'Rome', 'Berlin', 'Sydney']

# Replacing the last two cities with new ones
cities[-2:] = ["Dubai", "Cape Town"]
print(cities)  # Output: ['Paris', 'Tokyo', 'Rome', 'Dubai', 'Cape Town']
copy

In this example:

  1. We replaced the city "New York" at index 3 with "Rome";
  2. Using negative indexing, we replaced the last two cities ("Rome" and "Sydney") with "Dubai" and "Cape Town".

You can also make multiple changes in one step:


              
123456

            
cities = ["Paris", "Tokyo", "New York", "Berlin", "Sydney"]

# Replacing multiple cities in the middle
cities[1:3] = ["Seoul", "Bangkok", "Mumbai"]

print(cities)  # Output: ['Paris', 'Seoul', 'Bangkok', 'Mumbai', 'Berlin', 'Sydney']
copy

Here, we replaced "Tokyo" and "New York" with three cities: "Seoul", "Bangkok", and "Mumbai". This demonstrates how flexible list mutability can be for managing your data.

Uppgift

Swipe to start coding

You have a travel_wishlist list.

  • Update the estimated cost of all cities to include a discount.
  • Apply a 20% reduction to the cost (the third element in the nested list).
  • Use indexing to update the elements.

Lösning

Switch to desktopByt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan
Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 5
Switch to desktopByt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan
Vi beklagar att något gick fel. Vad hände?
some-alt