In this article we will discuss different ways to convert a single or multiple lists to dictionary in Python.

Following conversions from list to dictionary will be covered here,

  • Convert a List to Dictionary with same values
  • Convert List items as keys in dictionary with enumerated value
  • Convert two lists to dictionary
  • Convert a list of tuples to dictionary

Convert a List to Dictionary with same values

Suppose we have a list of strings i.e.

# List of strings
listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ]

Now we want to create a dictionary with all elements in this list as keys. For each key value will be same i.e. 5. Let’s see how to do that i.e.

Using dictionary comprehension

'''
Converting a list to dictionary with list elements as keys in dictionary
All keys will have same value
''' 
dictOfWords = { i : 5 for i in listOfStr }

Dictionary contents will be,
hello  ::  5
here  ::  5
this  ::  5
test  ::  5
at  ::  5
now  ::  5

Using dict.fromKeys()
'''
Converting a list to dictionary with list elements as keys in dictionary
using dict.fromkeys()
''' 
dictOfWords = dict.fromkeys(listOfStr , 1)

dict.fromKeys() accepts a list and default value. It returns a dictionary with items in list as keys. All dictionary items will have same value, that was passed in fromkeys().

If no default value was passed in fromKeys() then default value for keys in dictionary will be None.

Convert List items as keys in dictionary with enumerated value

Suppose we have a list of strings i.e.

# List of strings
listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ]

Let’s create a dictionary from this list with list elements as keys and values as integers from 0 to n-1 (n is size of list) i.e.
'''
Converting a list to dictionary with list elements as values in dictionary
and keys are enumerated index starting from 0 i.e. index position of element in list
''' 
dictOfWords = { i : listOfStr[i] for i in range(0, len(listOfStr) ) }

Dictionary contents will be,
0  ::  hello
1  ::  at
2  ::  test
3  ::  this
4  ::  here
5  ::  now

Convert two lists to a dictionary

Suppose we have two lists i.e.

# List of strings
listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ]
    
# List of ints
listOfInt = [56, 23, 43, 97, 43, 102]

Let’s create a dictionary with elements of listOfStr as keys and elements of listOfInt as values using zip() i.e
# Create a zip object from two lists
zipbObj = zip(listOfStr, listOfInt)

# Create a dictionary from zip object
dictOfWords = dict(zipbObj)

Zip() accepts a number of iterable objects and returns a list of tuples. Each entry in tuple contains an element from each iterable object.
We have passed two lists objects in zip() , so it will return a list of tuples, where each tuple contains an entry from both the lists. Then we created a dictionary object from this list of tuples.

Dictionary contents are,

Dictionary from two Lists 
hello  ::  56
here  ::  43
this  ::  97
test  ::  43
at  ::  23
now  ::  102

  • If length of keys list is less than list of values then remaining elements in value list will be skipped.

Convert a list of tuples to dictionary

Suppose we have a list of tuples with two columns in each entry i.e.

# List of tuples    
listofTuples = [("Riti" , 11), ("Aadi" , 12), ("Sam" , 13),("John" , 22),("Lucy" , 90)]

We can directly pass this list of tuples to dictionary constructor i.e
# Convert a list of tuple to dictionary
studentsDict = dict(listofTuples)

Entries in first column will become the key and entries in second column will the values in the new dictionary. Contents of dictionary will be,
Dictionary from List of Tuples
John  ::  22
Lucy  ::  90
Riti  ::  11
Aadi  ::  12
Sam  ::  13

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,

'''
Display contents of dictionary with each key/value pair in seperate line
'''
def displatDict(text, dictOfElements) :
    print("*************")
    print(text)
    for key , value in dictOfElements.items():
        print(key, " :: ", value)

def main():
    
    
    # List of strings
    listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ]


    '''
    Converting a list to dictionary with list elements as keys in dictionary
    All keys will have same value
    ''' 
    dictOfWords = { i : 5 for i in listOfStr }
    
    displatDict("Dictionary with same value " , dictOfWords)   

    '''
    Converting a list to dictionary with list elements as keys in dictionary
    using dict.fromkeys()
    ''' 
    
    dictOfWords = dict.fromkeys(listOfStr , 1)
    
    displatDict("Dictionary with given default value " , dictOfWords) 
    
    dictOfWords = dict.fromkeys(listOfStr)
    
    displatDict("Dictionary with same default value None " , dictOfWords)

    
    '''
    Converting a list to dictionary with list elements as values in dictionary
    and keys are enumerated index starting from 0 i.e. index position of element in list
    ''' 
    dictOfWords = { i : listOfStr[i] for i in range(0, len(listOfStr) ) }
    
    
    displatDict("Dictionary with enumerated keys" , dictOfWords)
    
    
    
    '''
    Converting multiple lists to dictionary using zip
    list1 will be used as keys and list2 as values
    ''' 
    
    # List of strings
    listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ]
        
    # List of ints
    listOfInt = [56, 23, 43, 97, 43, 102]
    
    # Create a zip object from two lists
    zipbObj = zip(listOfStr, listOfInt)
    
    # Create a dictionary from zip object
    dictOfWords = dict(zipbObj)
    
    displatDict("Dictionary from two Lists " , dictOfWords)
    
    '''
    If list of keys is greater than list of values then extra keys will be skipped
    '''
    
    # List of strings
    listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ]
 
    # List of ints
    listOfInt = [56, 23, 43, 97, 43]
    
    zipbObj = zip(listOfStr, listOfInt)
    
    dictOfWords = dict(zipbObj)
    
    displatDict("Dictionary from two Lists " , dictOfWords)
    
    '''
    Convert a list of tuples to Dictionary
    '''

    # List of tuples    
    listofTuples = [("Riti" , 11), ("Aadi" , 12), ("Sam" , 13),("John" , 22),("Lucy" , 90)]
    
    # Convert a list of tuple to dictionary
    studentsDict = dict(listofTuples)
        
    displatDict("Dictionary from List of Tuples" , studentsDict)
   
            
            
if __name__ == '__main__':
    main()


Output
*************
Dictionary with same value 
now  ::  5
here  ::  5
test  ::  5
at  ::  5
this  ::  5
hello  ::  5
*************
Dictionary with given default value 
now  ::  1
here  ::  1
test  ::  1
at  ::  1
this  ::  1
hello  ::  1
*************
Dictionary with same default value None 
now  ::  None
here  ::  None
test  ::  None
at  ::  None
this  ::  None
hello  ::  None
*************
Dictionary with enumerated keys
0  ::  hello
1  ::  at
2  ::  test
3  ::  this
4  ::  here
5  ::  now
*************
Dictionary from two Lists 
now  ::  102
here  ::  43
test  ::  43
at  ::  23
this  ::  97
hello  ::  56
*************
Dictionary from two Lists 
test  ::  43
at  ::  23
this  ::  97
hello  ::  56
here  ::  43
*************
Dictionary from List of Tuples
John  ::  22
Lucy  ::  90
Riti  ::  11
Aadi  ::  12
Sam  ::  13

 

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