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一文掌握Python中列表

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前言:

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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 numbersnumbers = [1, 2, 3, 4, 5]# Example of a list of stringsfruits = ["apple", "banana", "cherry"]# Example of a mixed-type listmixed = [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: 1second_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 listfruits = ["apple", "banana"]fruits.append("cherry")  # fruits is now ["apple", "banana", "cherry"]# Insert: Adds an element at a specific indexfruits.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 valuefruits = ["apple", "banana", "cherry", "banana"]fruits.remove("banana")  # fruits is now ["apple", "cherry", "banana"]# Pop: Removes and returns the element at a specific indexremoved_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 listdel mylist[0] # deleting the first elemetdel 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# orcopy_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 ordernumbers.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 elementselement = nested_list[1][1]  # element is 5# Modifying elementsnested_list[0][2] = 10  # nested_list is now [[1, 2, 10], [4, 5, 6], [7, 8, 9]]# Adding a new inner listnew_inner_list = [11, 12, 13]nested_list.append(new_inner_list)# Removing an inner listnested_list.remove([4, 5, 6])# Displaying the nested listfor inner_list in nested_list:    print(inner_list)

输出量:

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

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