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Iterate through list of dictionaries in Python

  • Last Updated : 22 Nov, 2021

In this article, we will learn how to iterate through a list of dictionaries. 

List of dictionaries in use:

[{‘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’}]

Method 1: Using indexing

This is a direct method, where list elements are extracted using just the index.

Syntax:

list[index]

Example:

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])

Output:

{‘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’}

After using indexing to particular dictionaries, now we can treat each item of the list as a dictionary,

Example: Extracting values from a particular dictionary

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"
    }
]
 
for key, val in languages[0].items():
    print("{} : {}".format(key, val))

Output:

Python : Machine Learning

R : Machine learning

Method 2: Using keys()

After iterating to a list the keys from the dictionary can further be extracted using the keys() function.

Example: Extracting key values

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"
    }
]
 
# 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("-------------")

Output:

Python

R

————-

Python

Java Script

HTML

————-

C++

Python

————-

Java

Kotlin

————-

Method 3: Using list comprehension 

The list is simply iterated using list comprehension and the dictionaries are printed.

Example: Extracting keys using list comprehension

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"
    }
]
 
# here we are printing the keys of the dictionary
# 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")

Output:

Python

R

Python

Java Script

HTML

C++

Python

Java

Kotlin


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