In Python you can use a lambda function with sorted() to sort lists based on custom rules. It’s a concise way to define sorting logic inline without writing a separate function.
This is useful when working with dynamic sorting, anonymous logic or handling structured data like dictionaries and tuples.
Common Python Sorting Scenarios Using Lambda
Here are 5 practical ways to sort items in Python using lambda — with examples for numbers, tuples, dictionaries and reverse sorting.
1. Sort a List of Numbers (Default)
Sorts the list elements in ascending order based on their natural order (from smallest to largest) using the default comparison method.
numbers = [5, 2, 9, 1]
sorted_numbers = sorted(numbers)
print(sorted_numbers) # Output: [1, 2, 5, 9]
2. Sort with Lambda – Custom Key
Use lambda to create custom sort behavior dynamically — like sorting in reverse, by length or by any transformation of the data.
numbers = [5, 2, 9, 1]# Sort by the negative value to reverse using lambda
sorted_numbers = sorted(numbers, key=lambda x: -x)
print(sorted_numbers) # Output: [9, 5, 2, 1]
Also Read: Python’s Role in Shaping the Future of AI & ML in 2025
3. Sort List of Tuples
Sorts a list of tuples based on a particular index, like sorting alphabetically by the second value in each tuple.
items = [(1, 'apple'), (3, 'banana'), (2, 'cherry')]# Sort by second item in each tuple
sorted_items = sorted(items, key=lambda x: x[1])
print(sorted_items) # Output: [(1, 'apple'), (3, 'banana'), (2, 'cherry')]
4. Sort List of Dictionaries by Field
Sorts a list of dictionaries by a chosen field key, useful for organizing user data, records or API responses.
people = [ {"name": "Alice", "age": 30},
{"name": "Bob", "age": 25},
{"name": "Charlie", "age": 35}
]
# Sort by age
sorted_people = sorted(people, key=lambda person: person["age"])
print(sorted_people)
5. Sort in Reverse Order
Use lambda with the reverse=True flag to sort items from highest to lowest or from Z to A based on custom logic.
words = ['banana', 'apple', 'cherry']sorted_words = sorted(words, key=lambda x: x, reverse=True)
print(sorted_words) # Output: ['cherry', 'banana', 'apple']
Tip
lambda is good for quick inline sorting. Use regular functions (def) when logic gets complex or needs to be reused.
Also,
- sorted() returns a new sorted list
- .sort() modifies the list in place and works only on lists
