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This tutorial shows how to convert two lists into dictionaries in Python, where one list contains the keys and the other contains the values.

Convert two lists to dictionaries using zip()and in Pythondict()

Python has a built-in function zip()that aggregates iterable data types into a tuple and returns it to the caller. Function dict()Creates a dictionary from a given collection.

key_list = ["name", "age", "address"]
value_list = ["Johnny", "27", "New York"]

dict_from_list = dict(zip(key_list, value_list))
print(dict_from_list)

In this solution, we can convert a list to a dictionary using just one line and two functions.

Output:

{'name': 'Johnny', 'age': '27', 'address': 'New York'}

Convert a list to a dictionary using dictionary comprehension in Python

Dictionary comprehensions are a way to shorten the initialization time of creating dictionaries in Python. Comprehensions are foran alternative to loops, which require multiple lines and variables. Comprehensions do the initialization work in one line.

In this solution, the function zip()will still provide values ​​to the dictionary comprehension. The comprehension will zip()return the key-value pairs for each successive element within the return value of the function as a dictionary.

key_list = ["name", "age", "address"]
value_list = ["Johnny", "27", "New York"]

dict_from_list = {k: v for k, v in zip(key_list, value_list)}
print(dict_from_list)

Another way to convert lists to dictionaries is to use the indexing of the lists, use range()the function to iterate over both lists, and use a comprehension to build a dictionary from the lists.

It assumes that the length of the key list and the value list are the same. In this example, the length of the key list will be the basis for the range.

key_list = ["name", "age", "address"]
value_list = ["Johnny", "27", "New York"]

dict_from_list = {key_list[i]: value_list[i] for i in range(len(key_list))}
print(dict_from_list)

Both comprehension options will give the same output as the previous example.

The only difference between the two solutions is that one uses zip()the function to convert the list into a tuple. The other uses range()the function to iterate over both lists using the current index, forming a dictionary.

Output:

{'name': 'Johnny', 'age': '27', 'address': 'New York'}

forConvert a list to a dictionary using loop in Python

The most straightforward way to implement list-to-dictionary conversion is with a loop. Although this method is the least efficient and most verbose, it is a good place to start, especially if you are a beginner and want to understand more basic programming syntax.

Before the loop, initialize an empty dictionary. Afterwards, proceed with the transformation, which will require a nested loop; the outer loop will iterate over the list of keys, while the inner loop will iterate over the list of values.

key_list = ["name", "age", "address"]
value_list = ["Johnny", "27", "New York"]

dict_from_list = {}
for key in key_list:
    for value in value_list:
        dict_from_list[key] = value
        value_list.remove(value)
        break

print(dict_from_list)

Each time a key-value pair is formed, the value element is removed from the list so that the next key is assigned the next value. After the removal, the inner loop is interrupted and the next key is continued.

Another solution using a loop is to use range()to take advantage of the index to get the key and value pairs, as we did in the dictionary comprehension example.

key_list = ["name", "age", "address"]
value_list = ["Johnny", "27", "New York"]

dict_from_list = {}
for i in range(len(key_list)):
    dict_from_list[key_list[i]] = value_list[i]

print(dict_from_list)

Both solutions will produce the same output.

{"name": "Johnny", "age": "27", "address": "New York"}

To summarize, the most efficient way to convert two lists into a dictionary is to use the built-in function zip()to convert the two lists into a tuple, and then use dict()to convert the tuple into a dictionary.

Using dictionary comprehensions you can also zip()convert a list to a tuple using , or range()convert a list to a dictionary using , which iterates over and initializes a dictionary using the list's indices.

Both of these solutions are much better solutions than the naive solution which uses a normal loop to convert the list to a dictionary.