To sort a dictionary by its values in Python, you can use the sorted() function along with a key parameter. Here’s how to do it in both ascending and descending order, with explanations:
1. Sort by Value (Ascending Order)
my_dict = {'apple': 5, 'banana': 2, 'cherry': 8}
# Step 1: Convert dictionary items to a sorted list of tuples
sorted_items = sorted(my_dict.items(), key=lambda x: x[1])
# Step 2: Convert the sorted list back into a dictionary
sorted_dict = dict(sorted_items)
print(sorted_dict)
# Output: {'banana': 2, 'apple': 5, 'cherry': 8}2. Sort by Value (Descending Order)
sorted_items_desc = sorted(my_dict.items(), key=lambda x: x[1], reverse=True)
sorted_dict_desc = dict(sorted_items_desc)
print(sorted_dict_desc)
# Output: {'cherry': 8, 'apple': 5, 'banana': 2}3. Using operator.itemgetter (Faster for Large Data)
The operator module can improve performance for large datasets:
from operator import itemgetter
sorted_items = sorted(my_dict.items(), key=itemgetter(1))
sorted_dict = dict(sorted_items)4. Handling Older Python Versions (<3.7)
For versions where dictionaries do not preserve order, use collections.OrderedDict:
from collections import OrderedDict
sorted_items = sorted(my_dict.items(), key=lambda x: x[1])
ordered_dict = OrderedDict(sorted_items)Key Notes
- Dictionary Order: Python 3.7+ preserves insertion order, so the sorted result will maintain the new order.
- Immutable Result: Dictionaries themselves are not sorted in-place; a new sorted dictionary is created.
- Complex Values: Works with any comparable values (e.g., numbers, strings, dates).
Example Workflow
# Original dictionary
scores = {'Alice': 90, 'Bob': 75, 'Charlie': 85}
# Sort by ascending scores
sorted_scores = dict(sorted(scores.items(), key=lambda x: x[1]))
print(sorted_scores)
# Output: {'Bob': 75, 'Charlie': 85, 'Alice': 90}Summary
| Method | Use Case | Example Code |
|---|---|---|
sorted() + lambda | Simple value sorting | sorted(d.items(), key=lambda x: x[1]) |
operator.itemgetter | Faster for large datasets | sorted(d.items(), key=itemgetter(1)) |
OrderedDict | Pre-Python 3.7 compatibility | OrderedDict(sorted(d.items(), key=...)) |
By following these steps, you can efficiently sort dictionaries by their values in Python!