python : How to create a list of all the keys in the Dictionary ?

In this article we will discuss how to create a list of all keys in a dictionary.

Suppose we have a dictionary of string and integers i.e.

# Dictionary of string and int
wordFreqDic = {
    "Hello": 56,
    "at" : 23 ,
    "test" : 43,
    "this" : 78,
    "here" : 18,
    "city" : 2,
    }

Now how to get all the keys from above dictionary in a list  i.e.

['city', 'test', 'at', 'Hello', 'this', 'here']

Creating a list of all keys in dictionary using dict.keys()

In python, dictionary class provides a member function i.e.

dict.keys()

It returns a view object or iterator to the list of all keys in dictionary.  We can use this object for iteration or creating new list. Let’s use that to get the list of all keys in the above dictionary.

# Create a new list from the view object returned by keys() 
dictkeys = list (wordFreqDic.keys())

dictkeys content will be,

['city', 'test', 'at', 'Hello', 'this', 'here']

Creating a filtered list of dictionary keys using List Comprehension

Suppose from above mentioned dictionary, we want a list of keys that start with character ‘t’ only i.e.

['test', 'this']

let’s do that using for loop i.e.

dictkeys = list()

# Creating a list of keys that start with 't'     
for x in wordFreqDic :
    if x.startswith('t') :
        dictkeys.append(x)

dictkeys content will be,

['test', 'this']

But that’s not pythonic. Let’s do that using list comprehension,

# Creating a list of keys that start with 't'        
dictkeys = [x for x in wordFreqDic if x.startswith('t')]

dictkeys content will be,

['test', 'this']

Python Dictionary Tutorial - Series:

1. What is a Dictionary in Python & why do we need it?

2. Creating Dictionaries in Python

3. Iterating over dictionaries

4. Check if a key exists in dictionary

5. Check if a value exists in dictionary

6. Get all the keys in Dictionary

7. Get all the Values in a Dictionary

8. Remove a key from Dictionary

9. Add key/value pairs in Dictionary

10. Find keys by value in Dictionary

11. Filter a dictionary by conditions

12. Print dictionary line by line

13. Convert a list to dictionary

14. Sort a Dictionary by key

15. Sort a dictionary by value in descending or ascending order

16. Dictionary: Shallow vs Deep Copy

17. Remove keys while Iterating

18. Get all keys with maximum value

19. Merge two or more dictionaries in python

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Complete example is as follows,

def main():
    
    # Dictionary of string and int
    wordFreqDic = {
        "Hello": 56,
        "at" : 23 ,
        "test" : 43,
        "this" : 78,
        "here" : 18,
        "city" : 2,
        }

    print("Dictionary : ", wordFreqDic)
    
    '''
    Creating a list of keys in dictionary
    '''
    
    # Create a new list from the view object returned by keys() 
    dictkeys = list (wordFreqDic.keys())
    
    print("List of keys in Dictionary : ", dictkeys)
    
    
    '''
    Creating a filtered list of keys in dictionary using for loop
    '''
    
    dictkeys = list()
    
    # Creating a list of keys that start with 't'     
    for x in wordFreqDic :
        if x.startswith('t') :
            dictkeys.append(x)
     
    print("List of keys in Dictionary that start with 't' : " , dictkeys)
    
    '''
    Creating a filtered list of keys in dictionary using List comprehension
    '''
    
    # Creating a list of keys that start with 't'        
    dictkeys = [x for x in wordFreqDic if x.startswith('t')]
    
    print("List of keys in Dictionary that start with 't' : " , dictkeys)

    
if __name__ == '__main__':
    main()

Output:

Dictionary :  {'city': 2, 'test': 43, 'at': 23, 'Hello': 56, 'this': 78, 'here': 18}
List of keys in Dictionary :  ['city', 'test', 'at', 'Hello', 'this', 'here']
List of keys in Dictionary that start with 't' :  ['test', 'this']
List of keys in Dictionary that start with 't' :  ['test', 'this']

 

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