Sort a dictionary by value in Python
David Y.
The Problem
How can I sort a dictionary by value in Python?
The Solution
Python dictionaries were originally intended to be used for data that does not have a meaningful order. In older versions of Python, no order is guaranteed. However, as of Python 3.7, key-value pairs in Python dictionaries are ordered according to when they were inserted. This means that we can sort a dictionary by sorting its key-value pairs and creating a new dictionary from them. The code below shows how to do this:
prices = {"Orange": 3, "Avocado": 5, "Apple": 1, "Pear": 2, "Grapefruit": 4} prices_sorted = dict(sorted(prices.items(), key=lambda item: item[1])) print(prices_sorted) # will output {"Apple": 1, "Pear": 2, "Orange": 3, "Grapefruit": 4, "Avocado": 5}
Here we use Python’s built-in sorted() function to sort our dictionary’s items (i.e. its key-value pairs) by value, ascending. We then convert the output of sorted(), which will be a list of tuples, into a new dictionary. As items will be inserted into our new dictionary in order of their values, we now have a dictionary ordered by value.
In older versions of Python, we would need to use an OrderedDict from Python’s built-in collections module in place of an ordinary dictionary, as shown below:
from collections import OrderedDict prices = {"Orange": 3, "Avocado": 5, "Apple": 1, "Pear": 2, "Grapefruit": 4} prices_sorted = OrderedDict(sorted(prices.items(), key=lambda item: item[1])) print(prices_sorted) # will output OrderedDict([("Apple", 1), ("Pear", 2), ("Orange", 3), ("Grapefruit", 4), ("Avocado", 5)])
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