列表(Lists)就像用其他语言声明的数组一样。列表不一定总是同质的，这使其成为Python中最强大的工具。单个列表可能包含数据类型，例如整数，字符串以及对象。列表是可变的，因此即使在创建后也可以对其进行更改。
Python中的List是有序的，并且有一个确定的计数。列表中的元素按照一定的顺序进行索引，并且列表的索引是在0为第一个索引的情况下完成的。列表中的每个元素在列表中都有其明确的位置，这允许复制列表中的元素，每个元素都有其独特的位置和可信度。
注意：列表是用于保留数据序列并对其进行进一步迭代的有用工具。
创建列表
Python中的列表可以通过将序列放在方括号[]中来创建。与集合不同，list不需要内置函数来创建list。
注意：与集合不同，列表可能包含可变元素。
# Python program to demonstrate # Creation of List # Creating a List List = [] print("Intial blank List: ") print(List) # Creating a List with # the use of a String List = ['GeeksForGeeks'] print("List with the use of String: ") print(List) # Creating a List with # the use of multiple values List = ["Geeks", "For", "Geeks"] print("List containing multiple values: ") print(List[0]) print(List[2]) # Creating a Multi-Dimensional List # (By Nesting a list inside a List) List = [['Geeks', 'For'] , ['Geeks']] print("Multi-Dimensional List: ") print(List)
输出：
Intial blank List: []List with the use of String: ['GeeksForGeeks']List containing multiple values: GeeksGeeksMulti-Dimensional List: [['Geeks', 'For'], ['Geeks']]
创建包含多个不同或重复元素的列表
列表可能包含具有不同位置的重复值，因此，在创建列表时，可以将多个不同或重复的值作为序列传递。
# Creating a List with # the use of Numbers # (Having duplicate values) List = [1, 2, 4, 4, 3, 3, 3, 6, 5] print("List with the use of Numbers: ") print(List) # Creating a List with # mixed type of values # (Having numbers and strings) List = [1, 2, 'Geeks', 4, 'For', 6, 'Geeks'] print("List with the use of Mixed Values: ") print(List)
输出：
List with the use of Numbers: [1, 2, 4, 4, 3, 3, 3, 6, 5]List with the use of Mixed Values: [1, 2, 'Geeks', 4, 'For', 6, 'Geeks']
向列表中添加元素
使用append()方法
可以使用内置的append()函数将元素添加到列表中。使用append()方法一次只能向列表中添加一个元素，如果使用append()方法添加多个元素，则使用循环。元组也可以使用append方法添加到列表中，因为元组是不可变的。与集合不同，还可以使用append()方法将列表添加到现有列表中。
# Python program to demonstrate # Addition of elements in a List # Creating a List List = [] print("Initial blank List: ") print(List) # Addition of Elements # in the List List.append(1) List.append(2) List.append(4) print("List after Addition of Three elements: ") print(List) # Adding elements to the List # using Iterator for i in range(1, 4):List.append(i) print("List after Addition of elements from 1-3: ") print(List) # Adding Tuples to the List List.append((5, 6)) print("List after Addition of a Tuple: ") print(List) # Addition of List to a List List2 = ['For', 'Geeks'] List.append(List2) print("List after Addition of a List: ") print(List)
输出：
Initial blank List: []List after Addition of Three elements: [1, 2, 4]List after Addition of elements from 1-3: [1, 2, 4, 1, 2, 3]List after Addition of a Tuple: [1, 2, 4, 1, 2, 3, (5, 6)]List after Addition of a List: [1, 2, 4, 1, 2, 3, (5, 6), ['For', 'Geeks']]
使用insert()方法
append()方法只适用于在列表末尾添加元素，对于在所需位置添加元素，则使用insert()方法。与只接受一个参数的append()不同，insert()方法需要两个参数(位置、值)。
# Python program to demonstrate # Addition of elements in a List # Creating a List List = [1,2,3,4] print("Initial List: ") print(List) # Addition of Element at # specific Position # (using Insert Method) List.insert(3, 12) List.insert(0, 'Geeks') print("List after performing Insert Operation: ") print(List)
输出：
Initial List: [1, 2, 3, 4]List after performing Insert Operation: ['Geeks', 1, 2, 3, 12, 4]
使用extend()方法
除了append()和insert()方法之外，还有一个用于添加元素的方法extend()，该方法用于在列表末尾同时添加多个元素。
注意：append()和extend()方法只能在末尾添加元素。
# Python program to demonstrate # Addition of elements in a List# Creating a List List = [1,2,3,4] print("Initial List: ") print(List) # Addition of multiple elements # to the List at the end # (using Extend Method) List.extend([8, 'Geeks', 'Always']) print("List after performing Extend Operation: ") print(List)
输出：
Initial List: [1, 2, 3, 4]List after performing Extend Operation: [1, 2, 3, 4, 8, 'Geeks', 'Always']
访问列表中的元素
要访问列表项，请参考索引号。使用索引运算符[]访问列表中的项。索引必须是整数。使用嵌套索引访问嵌套列表。
# Python program to demonstrate # accessing of element from list # Creating a List with # the use of multiple values List = ["Geeks", "For", "Geeks"] # accessing a element from the # list using index number print("Accessing a element from the list") print(List[0]) print(List[2]) # Creating a Multi-Dimensional List # (By Nesting a list inside a List) List = [['Geeks', 'For'] , ['Geeks']] # accessing a element from the # Multi-Dimensional List using # index number print("Acessing a element from a Multi-Dimensional list") print(List[0][1]) print(List[1][0])
输出：
Accessing a element from the listGeeksGeeksAcessing a element from a Multi-Dimensional listForGeeks
负索引
在Python中，负序列索引表示数组末尾的位置。不必像List[len(List)-3]那样计算偏移量，只需编写List[-3]就足够了。负索引意味着从结尾开始，-1表示最后一项，-2表示第二个最后项等。
List = [1, 2, 'Geeks', 4, 'For', 6, 'Geeks'] # accessing a element using # negative indexing print("Acessing element using negative indexing") # print the last element of list print(List[-1]) # print the third last element of list print(List[-3])
输出：
Acessing element using negative indexingGeeksFor
从列表中删除元素
使用remove()方法
可以使用内置的remove()函数从列表中删除元素，但是如果元素不存在于集合中，则会发生错误。Remove()方法一次只删除一个元素，要删除元素范围，则使用迭代器。remove()方法删除指定的项目。
注意：列表中的Remove方法将只删除搜索到的元素的第一个匹配项。
# Python program to demonstrate # Removal of elements in a List # Creating a List List = [1, 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12] print("Intial List: ") print(List) # Removing elements from List # using Remove() method List.remove(5) List.remove(6) print("List after Removal of two elements: ") print(List) # Removing elements from List # using iterator method for i in range(1, 5):List.remove(i) print("List after Removing a range of elements: ") print(List)
输出：
Intial List: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]List after Removal of two elements: [1, 2, 3, 4, 7, 8, 9, 10, 11, 12]List after Removing a range of elements: [7, 8, 9, 10, 11, 12]
使用pop()方法
Pop()函数还可以用于从集合中移除和返回元素，但默认情况下，它只移除集合的最后一个元素。若要从列表的特定位置移除元素，元素的索引将作为参数传递给Pop()方法。
List = [1,2,3,4,5] # Removing element from the # Set using the pop() method List.pop() print("List after popping an element: ") print(List) # Removing element at a # specific location from the # Set using the pop() method List.pop(2) print("List after popping a specific element: ") print(List)
输出：
List after popping an element: [1, 2, 3, 4]List after popping a specific element: [1, 2, 4]
列表切片(Slicing of a List)
在Python List中，有多种方法可以打印包含所有元素的整个列表，但是要从列表中打印特定范围的元素，我们使用Slice操作。切片操作在使用冒号(：)的列表上执行。若要从开始到范围打印元素，请使用[：Index]；若要从结束使用[：-Index]打印元素；若要从特定索引打印元素，直到结束使用[Index:]；若要打印范围内的元素，请使用[开始索引：结束索引]；若要使用切片操作打印整个列表，请使用[：]。此外，要按相反顺序打印整个列表，请使用[：：-1]。
注意：要从后端打印列表元素，请使用负索引。
# Python program to demonstrate # Removal of elements in a List # Creating a List List = ['G','E','E','K','S','F', 'O','R','G','E','E','K','S'] print("Intial List: ") print(List) # Print elements of a range # using Slice operation Sliced_List = List[3:8] print("Slicing elements in a range 3-8: ") print(Sliced_List) # Print elements from a # pre-defined point to end Sliced_List = List[5:] print("Elements sliced from 5th ""element till the end: ") print(Sliced_List) # Printing elements from # beginning till end Sliced_List = List[:] print("Printing all elements using slice operation: ") print(Sliced_List)
输出：
Intial List: ['G', 'E', 'E', 'K', 'S', 'F', 'O', 'R', 'G', 'E', 'E', 'K', 'S']Slicing elements in a range 3-8: ['K', 'S', 'F', 'O', 'R']Elements sliced from 5th element till the end: ['F', 'O', 'R', 'G', 'E', 'E', 'K', 'S']Printing all elements using slice operation: ['G', 'E', 'E', 'K', 'S', 'F', 'O', 'R', 'G', 'E', 'E', 'K', 'S']
负索引列表切片
# Creating a List List = ['G','E','E','K','S','F', 'O','R','G','E','E','K','S'] print("Initial List: ") print(List) # Print elements from beginning # to a pre-defined point using Slice Sliced_List = List[:-6] print("Elements sliced till 6th element from last: ") print(Sliced_List) # Print elements of a range # using negative index List slicing Sliced_List = List[-6:-1] print("Elements sliced from index -6 to -1") print(Sliced_List) # Printing elements in reverse # using Slice operation Sliced_List = List[::-1] print("Printing List in reverse: ") print(Sliced_List)
输出：
Initial List: ['G', 'E', 'E', 'K', 'S', 'F', 'O', 'R', 'G', 'E', 'E', 'K', 'S']Elements sliced till 6th element from last: ['G', 'E', 'E', 'K', 'S', 'F', 'O']Elements sliced from index -6 to -1['R', 'G', 'E', 'E', 'K']Printing List in reverse: ['S', 'K', 'E', 'E', 'G', 'R', 'O', 'F', 'S', 'K', 'E', 'E', 'G']
列表方法
带列表的内置函数
