如何在 Python 中迭代嵌套列表？

原文:https://www . geesforgeks . org/如何迭代 python 中的嵌套列表/

在本文中，我们将看到如何迭代嵌套列表。一个列表可以用来存储多种数据类型，如整数、字符串、对象，还可以在它自己的中另一个列表。列表中的这个子列表就是通常所说的嵌套列表。

遍历嵌套列表

让我们看看典型的嵌套列表是什么样子的:

有多种方法可以迭代嵌套列表:

方法 1: 使用索引遍历列表

正指数的使用:

Python 3

# code
list = [10, 20, 30, 40, [80, 60, 70]]

# Printing sublist at index 4
print(list[4])

# Printing 1st element of the sublist
print(list[4][0])

# Printing 2nd element of the sublist
print(list[4][1])

# Printing 3rd element of the sublist
print(list[4][2])

输出:

[80, 60, 70]
80
60
70

负指数的使用

Python 3

# code
list = [10, 20, 30, 40, [80, 60, 70]]

# Printing sublist at index 4
print(list[-1])

# Printing 1st element of the sublist
print(list[-1][-3])

# Printing 2nd element of the sublist
print(list[-1][-2])

# Printing 3rd element of the sublist
print(list[-1][-1])

输出:

[80, 60, 70]
80
60
70

方法 2: 使用循环遍历列表

Python 3

# code
# LIST
list = [["Rohan", 60], ["Aviral", 21], 
        ["Harsh", 30], ["Rahul", 40],
        ["Raj", 20]]

# looping through nested list using indexes
for names in list:
    print(names[0], "is", names[1],
          "years old.")

输出:

Rohan is 60 years old.
Aviral is 21 years old.
Harsh is 30 years old.
Rahul is 40 years old.
Raj is 20 years old.

在循环中使用临时变量。

Python 3

# code
# LIST
list = [["Rohan", 60], ["Aviral", 21], 
        ["Harsh", 30], ["Rahul", 40],
        ["Raj", 20]]

# looping through nested list using multiple 
# temporary variables
for name, age in list:
    print(name, "is",
          age, "years old.")

输出:

Rohan is 60 years old.
Aviral is 21 years old.
Harsh is 30 years old.
Rahul is 40 years old.
Raj is 20 years old.

方法 3: 切片的使用

Python 3

# code
# list
list = [10, 20, 30, 40,
        [80, 60, 70]]

# print the entire Sublist at index 4
print(list[4][:])

# printing first two element
print(list[4][0 : 2])

输出:

[80, 60, 70]
[80, 60]

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