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Lists in Python In Python, a list is a very versatile data structure used to store an ordered collection of elements. Lists are mutable, meaning you can modify them after creation, and they can contain elements of different types.
Creating Lists There are several ways to create lists in Python:
# Empty list lista_vacia = [] # List with numbers lista_numeros = [ 1 , 2 , 3 , 4 , 5 ] # Mixed data types lista_mezclada = [ 1 , "dos" , 3.0 , True ]
Lists can contain elements of different types including numbers, strings, booleans, and even other lists.
Accessing Elements You can access list elements using indices. Python uses zero-based indexing:
lista = [ "a" , "b" , "c" , "d" , "e" ] # Access first element primer_elemento = lista[ 0 ] # "a" # Access last element ultimo_elemento = lista[ - 1 ] # "e" # Slicing - get a sublist sublista = lista[ 1 : 4 ] # ["b", "c", "d"]
Understanding List Indexing
Positive indices start from 0 (beginning of list)
Negative indices start from -1 (end of list)
lista[start:end] returns elements from start up to (but not including) end
lista[:n] - first n elementslista[n:] - from index n to endlista[:] - copy of entire list Modifying Lists Change Individual Elements lista = [ 1 , 2 , 3 , 4 , 5 ] lista[ 2 ] = 10 # Changes the third element to 10 # Result: [1, 2, 10, 4, 5]
Adding Elements lista = [ 1 , 2 , 3 ] # Append - adds element to the end lista.append( 4 ) # [1, 2, 3, 4] # Extend - adds multiple elements from another list lista.extend([ 5 , 6 ]) # [1, 2, 3, 4, 5, 6] # Insert - adds element at specific position lista.insert( 2 , 10 ) # Inserts 10 at index 2
append() adds a single element, while extend() adds all elements from an iterable.
Removing Elements lista = [ 1 , 2 , 3 , 4 , 5 ] # Remove by value - removes first occurrence lista.remove( 3 ) # Removes the value 3 # Pop - removes and returns last element (or at specified index) elemento_eliminado = lista.pop() # Removes last element # Delete by index del lista[ 2 ] # Removes element at index 2
Practical Example: Family Members List Here’s a real-world example managing a family members list:
miembrosDeLaFamilia = [ "tatarabuelo" ] miembrosDeLaFamiliaExpulsado = [] # Adding members miembrosDeLaFamilia.append( "abuelo" ) miembrosDeLaFamilia.insert( 1 , "abuela" ) miembrosDeLaFamilia.append( "papa" ) miembrosDeLaFamilia.append( "mama" ) miembrosDeLaFamilia.append( "yo" ) print ( "ANTES:" , miembrosDeLaFamilia) # Output: ['tatarabuelo', 'abuela', 'abuelo', 'papa', 'mama', 'yo'] # Removing members del miembrosDeLaFamilia[ 2 ] miembrosDeLaFamilia.remove( "abuelo" ) miembrosDeLaFamiliaExpulsado.append(miembrosDeLaFamilia.pop( 2 )) print ( "DESPUES:" , miembrosDeLaFamilia) print ( "cantidad de miembros:" , len (miembrosDeLaFamilia)) print ( "miembros expulsado:" , miembrosDeLaFamiliaExpulsado)
Sorting Lists Sort In-Place The sort() method modifies the original list:
# Sort numbers numeros = [ 3 , 1 , 4 , 1 , 5 , 9 , 2 ] numeros.sort() print (numeros) # [1, 1, 2, 3, 4, 5, 9] # Sort strings alphabetically palabras = [ "zebra" , "manzana" , "banana" ] palabras.sort() print (palabras) # ['banana', 'manzana', 'zebra']
Sort Without Modifying Original Use the sorted() function to create a new sorted list:
original = [ 3 , 1 , 4 ] ordenada = sorted (original) print (original) # [3, 1, 4] - unchanged print (ordenada) # [1, 3, 4] - new sorted list
sort() modifies the list in-place and returns None. sorted() returns a new sorted list.
Iterating Over Lists You can loop through list elements using a for loop:
miembrosDeLaFamilia = [ "papa" , "mama" , "yo" ] for miembro in miembrosDeLaFamilia: print ( "#->" , miembro.upper()) # Output: # #-> PAPA # #-> MAMA # #-> YO
Common List Operations
lista = [ 1 , 2 , 3 , 4 , 5 ] print ( len (lista)) # 5
if "manzana" in frutas: print ( "Found!" )
lista = [ 1 , 2 , 2 , 3 , 2 , 4 ] print (lista.count( 2 )) # 3
lista = [ 10 , 20 , 30 , 40 ] print (lista.index( 30 )) # 2
Converting Between Lists and Tuples You can convert between lists and tuples:
# Tuple to list tuplaMesclada = ( "javier" , 234 , "javier" , "hola mundo" ) tuplaMesclada = list (tuplaMesclada) print (tuplaMesclada) # Now it's a list # List to tuple lista = [ 1 , 2 , 3 ] tupla = tuple (lista)
Key Takeaways
Lists are mutable - you can modify them after creation
Lists are ordered - elements maintain their insertion order
Lists allow duplicates - the same value can appear multiple times
Lists can contain mixed types - numbers, strings, booleans, objects, etc.
Lists support negative indexing - access elements from the end
Use lists when you need a collection that can grow, shrink, or change over time. For fixed collections, consider using tuples instead.