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Python | Convert a list to dictionary

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  • Difficulty Level : Medium
  • Last Updated : 03 Oct, 2022
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Given a list, write a Python program to convert the given list to dictionary such that all the odd elements have the key, and even number elements have the value. Since python dictionary is unordered, the output can be in any order.

Examples: 

Input : ['a', 1, 'b', 2, 'c', 3]
Output : {'a': 1, 'b': 2, 'c': 3}
Input : ['Delhi', 71, 'Mumbai', 42]
Output : {'Delhi': 71, 'Mumbai': 42}

Method #1: dict comprehension

To convert a list to dictionary, we can use list comprehension and make a key:value pair of consecutive elements. Finally, typecase the list to dict type. 

Python3




# Python3 program to Convert a
# list to dictionary
 
def Convert(lst):
    res_dct = {lst[i]: lst[i + 1] for i in range(0, len(lst), 2)}
    return res_dct
         
# Driver code
lst = ['a', 1, 'b', 2, 'c', 3]
print(Convert(lst))

Output

{'a': 1, 'b': 2, 'c': 3}

Method #2 : Using zip() method

First create an iterator, and initialize it to variable ‘it’. Then use zip method, to zip keys and values together. Finally typecast it to dict type. 

Python3




# Python3 program to Convert a
# list to dictionary
 
 
def Convert(a):
    it = iter(a)
    res_dct = dict(zip(it, it))
    return res_dct
 
 
# Driver code
lst = ['a', 1, 'b', 2, 'c', 3]
print(Convert(lst)

Output

{'a': 1, 'b': 2, 'c': 3}

Method #3: Using the map and dict method

First, create an array of keys and values by using array slicing. Then use the map method to form array of tuple with key value paris. Finally typecast it to dict type. 

Python




# Python3 program to Convert a
# list to dictionary
 
 
def Convert(lst):
    res_dct = map(lambda i: (lst[i], lst[i+1]), range(len(lst)-1)[::2])
    return dict(res_dct)
 
 
# Driver code
lst = ['a', 1, 'b', 2, 'c', 3]
print(Convert(lst))

Output

{'a': 1, 'c': 3, 'b': 2}

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