snippetpythonTip

Convert between lists and dictionaries

Submitted by: @import:30-seconds-of-code·Mar 2, 2026·

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Problem

To convert a dictionary to a list of tuples, use dict.items() and list() to get a list of tuples from the given dictionary.
In order to combine two lists into a dictionary, the elements of the first one will serve as the keys and the elements of the second one serve as the values.
The values of the first list need to be unique and hashable.
Given these preconditions, use zip() in combination with dict() to combine the values of the two lists into a dictionary.
If you want to map the values of a list to a dictionary using a function, where the key-value pairs consist of the original value as the key and the result of the function as the value, you can use a similar technique. Instead of simply using zip(), you can apply the function to each value of the list using map() before combining the values into a dictionary.

Solution

def dict_to_list(d):
  return list(d.items())

d = {'one': 1, 'three': 3, 'five': 5, 'two': 2, 'four': 4}
dict_to_list(d)
# [('one', 1), ('three', 3), ('five', 5), ('two', 2), ('four', 4)]

The values of the first list need to be unique and hashable.
Given these preconditions, use zip() in combination with dict() to combine the values of the two lists into a dictionary.
If you want to map the values of a list to a dictionary using a function, where the key-value pairs consist of the original value as the key and the result of the function as the value, you can use a similar technique. Instead of simply using zip(), you can apply the function to each value of the list using map() before combining the values into a dictionary.

Code Snippets

def dict_to_list(d):
  return list(d.items())

d = {'one': 1, 'three': 3, 'five': 5, 'two': 2, 'four': 4}
dict_to_list(d)
# [('one', 1), ('three', 3), ('five', 5), ('two', 2), ('four', 4)]

def to_dictionary(keys, values):
  return dict(zip(keys, values))

to_dictionary(['a', 'b'], [1, 2]) # { a: 1, b: 2 }

def map_dictionary(itr, fn):
  return dict(zip(itr, map(fn, itr)))

map_dictionary([1, 2, 3], lambda x: x * x) # { 1: 1, 2: 4, 3: 9 }

Context

From 30-seconds-of-code: dictionary-to-list

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