遍历Python中的字典列表

在本文中，我们将学习如何遍历字典列表。

使用中的字典列表：

[{‘Python’: ‘Machine Learning’, ‘R’: ‘Machine learning’}, 

{‘Python’: ‘Web development’, ‘Java Script’: ‘Web Development’, ‘HTML’: ‘Web Development’}, 

{‘C++’: ‘Game Development’, ‘Python’: ‘Game Development’}, {‘Java’: ‘App Development’, ‘Kotlin’: ‘App Development’}]

方法 1：使用索引

这是一种直接方法，其中仅使用索引提取列表元素。

句法：

list[index]

例子：

Python3

# Create a list of dictionaries
languages = [
    {
        "Python": "Machine Learning",
        "R": "Machine learning",
    },
    {
        "Python": "Web development",
        "Java Script": "Web Development",
        "HTML": "Web Development"
    },
    {
        "C++": "Game Development",
        "Python": "Game Development"
    },
    {
        "Java": "App Development",
        "Kotlin": "App Development"
    }
]
  
  
print(languages[0])
print(languages[1])
print(languages[2])
print(languages[3])

输出：

{‘Python’: ‘Machine Learning’, ‘R’: ‘Machine learning’}

{‘Python’: ‘Web development’, ‘Java Script’: ‘Web Development’, ‘HTML’: ‘Web Development’}

{‘C++’: ‘Game Development’, ‘Python’: ‘Game Development’}

{‘Java’: ‘App Development’, ‘Kotlin’: ‘App Development’}

在对特定字典使用索引后，现在我们可以将列表中的每个项目视为字典，

示例：从特定字典中提取值

蟒蛇3

# Create a list of dictionaries
languages = [
    {
        "Python": "Machine Learning",
        "R": "Machine learning",
    },
    {
        "Python": "Web development",
        "Java Script": "Web Development",
        "HTML": "Web Development"
    },
    {
        "C++": "Game Development",
        "Python": "Game Development"
    },
    {
        "Java": "App Development",
        "Kotlin": "App Development"
    }
]
  
for key, val in languages[0].items():
    print("{} : {}".format(key, val))

输出：

Python : Machine Learning

R : Machine learning

方法二：使用keys()

在迭代到列表之后，可以使用 keys()函数进一步提取字典中的键。

示例：提取键值

蟒蛇3

# Create a list of dictionaries
languages = [
    {
        "Python": "Machine Learning",
        "R": "Machine learning",
    },
    {
        "Python": "Web development",
        "Java Script": "Web Development",
        "HTML": "Web Development"
    },
    {
        "C++": "Game Development",
        "Python": "Game Development"
    },
    {
        "Java": "App Development",
        "Kotlin": "App Development"
    }
]
  
# iterate over the list
for i in languages:
    
    # now i is a dict, now we see the keys 
    # of the dict
    for key in i.keys():
        
        # print every key of each dict
        print(key)
  
    print("-------------")

输出：

Python

R

————-

Python

Java Script

HTML

————-

C++

Python

————-

Java

Kotlin

————-

方法 3：使用列表理解 

使用列表推导简单地迭代列表并打印字典。

示例：使用列表推导式提取键

蟒蛇3

# Create a list of dictionaries
languages = [
    {
        "Python" : "Machine Learning",
        "R" : "Machine learning",
    },
    {
        "Python" : "Web development",
        "Java Script" : "Web Development",
        "HTML" : "Web Development"
    },
    {
        "C++" : "Game Development",
        "Python" : "Game Development"
    },
    {
        "Java" : "App Development",
        "Kotlin" : "App Development"
    }
]
  
# here we are printing the keys of the dictonary 
# by using list comprehension and each key will be
# printed in a new line due to the presence of " sep = "\n" ".
# It will add a new line character to our output.
  
print(*[key for i in languages for key in i.keys()], sep = "\n")

输出：

Python

R

Python

Java Script

HTML

C++

Python

Java

Kotlin