创建列表

可以在Python中创建一个列表，方法是将一系列元素放在方括号（ [] ）中，用逗号分隔。

# Example of a list of numbers
numbers = [1, 2, 3, 4, 5]

# Example of a list of strings
fruits = ["apple", "banana", "cherry"]

# Example of a mixed-type list
mixed = [1, "hello", 3.14, True]

元素访问

可以使用列表中的元素的索引来访问它们。第一个元素的索引从0开始。

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

first_element = numbers[0]  # Output: 1
second_element = numbers[1]  # Output: 2

列表操作函数和方法

添加元素

可以使用各种方法向列表添加元素：

# Append: Adds an element to the end of the list
fruits = ["apple", "banana"]
fruits.append("cherry")  # fruits is now ["apple", "banana", "cherry"]

# Insert: Adds an element at a specific index
fruits.insert(1, "orange")  # fruits is now ["apple", "orange", "banana", "cherry"]

扩展列表

将元素从另一个列表移到当前列表的末尾。

fruits = ["apple", "banana"]
more_fruits = ["cherry", "orange"]
fruits.extend(more_fruits)  # fruits is now ["apple", "banana", "cherry", "orange"]

更改项目值

fruits = ["apple", "banana", "cherry", "banana"]
fruits[1]="melon"  # fruits is now ['apple', 'melon', 'cherry', 'banana']

fruits[1:3]=["pappaya","kiwi"] # fruits is now ['apple', 'pappaya', 'kiwi', 'banana']

移除元素

可以使用各种方法从列表中删除元素：

# Remove: Removes the first occurrence of a value
fruits = ["apple", "banana", "cherry", "banana"]
fruits.remove("banana")  # fruits is now ["apple", "cherry", "banana"]

# Pop: Removes and returns the element at a specific index
removed_element = fruits.pop(1)  # removed_element is "cherry", fruits is now ["apple", "banana"]

# clear : Removes all elements from the list, making it empty.
fruits = ["apple", "banana", "cherry"]
fruits.clear()  # fruits is now []

# del : deleting the elements or entire list
del mylist[0] # deleting the first elemet
del mylist # deleting the entire elemet

复制列表

创建列表的副本。

fruits = ["apple", "banana", "cherry"]
copy_fruits = fruits.copy()  # copy_fruits is a separate copy of fruits
# or
copy_fruits = fruits[:]  # Another way to create a copy of the list

逆转列表

反转列表中元素的顺序。

numbers = [1, 2, 3, 4, 5]
numbers.reverse()  # numbers is now [5, 4, 3, 2, 1]

排序列表

按升序对列表中的元素进行排序（默认情况下）。

numbers = [5, 1, 3, 2, 4]
numbers.sort()  # numbers is now [1, 2, 3, 4, 5]

# Sorting in descending order
numbers.sort(reverse = True)  # numbers is now [5, 4, 3, 2, 1]

计数

返回指定值在列表中出现的次数。

numbers = [1, 2, 3, 4, 2, 2, 5]
count = numbers.count(2)  # count is 3

嵌套列表

嵌套列表是包含其他列表作为其元素的列表。这允许创建列表的列表，提供了一种表示更复杂数据结构的方法。在Python中，你可以嵌套列表来创建多维数据结构。

nested_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

在这个例子中， nested_list 包含三个内部列表，每个列表代表一行数据：

[[1, 2, 3],
 [4, 5, 6],
 [7, 8, 9]]

以下是如何在Python中使用嵌套列表：

nested_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# Accessing elements
element = nested_list[1][1]  # element is 5

# Modifying elements
nested_list[0][2] = 10  # nested_list is now [[1, 2, 10], [4, 5, 6], [7, 8, 9]]

# Adding a new inner list
new_inner_list = [11, 12, 13]
nested_list.append(new_inner_list)

# Removing an inner list
nested_list.remove([4, 5, 6])

# Displaying the nested list
for inner_list in nested_list:
    print(inner_list)

输出量：

[1, 2, 10]
[7, 8, 9]
[11, 12, 13]