How do I sort a dictionary by key in Python?

To sort a dictionary by its keys in Python, you can use the following approaches, depending on your Python version and requirements:

1. For Python 3.7+ (Standard dict Preserves Insertion Order)

Convert the dictionary items to a sorted list of (key, value) tuples and create a new dictionary:

my_dict = {'banana': 3, 'apple': 4, 'pear': 1, 'orange': 2}

# Sort by keys and create a new dictionary
sorted_dict = dict(sorted(my_dict.items()))

print(sorted_dict)
# Output: {'apple': 4, 'banana': 3, 'orange': 2, 'pear': 1}

2. For Python <3.7 (Use collections.OrderedDict)

Use OrderedDict to maintain the sorted order:

from collections import OrderedDict

my_dict = {'banana': 3, 'apple': 4, 'pear': 1, 'orange': 2}

# Sort by keys and create an OrderedDict
sorted_dict = OrderedDict(sorted(my_dict.items()))

print(sorted_dict)
# Output: OrderedDict([('apple', 4), ('banana', 3), ('orange', 2), ('pear', 1)])

3. Return a Sorted List of Keys/Values (Without Creating a New Dict)

If you only need sorted keys or key-value pairs (not a dictionary):

# Sorted list of keys
sorted_keys = sorted(my_dict.keys())

# Sorted list of (key, value) tuples
sorted_items = sorted(my_dict.items())

4. Sort by Keys in Reverse Order

Add reverse=True to sort in descending order:

sorted_dict = dict(sorted(my_dict.items(), reverse=True))
# Output: {'pear': 1, 'orange': 2, 'banana': 3, 'apple': 4}

Key Notes

• Immutability: Dictionaries cannot be sorted in-place. A new ordered dictionary is created.
• Custom Sorting: For complex keys (e.g., case-insensitive strings), use the key parameter:

  # Case-insensitive sort for string keys
  sorted_dict = dict(sorted(my_dict.items(), key=lambda item: item[0].lower()))

• Efficiency: Sorting has a time complexity of O(n log n), where n is the number of items.

Example Workflow

# Original dictionary
my_dict = {'b': 2, 'a': 1, 'c': 3}

# Sort and create a new dictionary
sorted_dict = dict(sorted(my_dict.items()))

print(sorted_dict)  # {'a': 1, 'b': 2, 'c': 3}

Summary

• Python 3.7+: Use dict(sorted(my_dict.items())).
• Legacy Python: Use OrderedDict(sorted(my_dict.items())).
• Reverse Order: Add reverse=True to the sorted() function.