Common Python List Operations: Sorting, Filtering, Searching, Merging, and More

1. Sort a list by ID – Given an API that returns a list of objects, the list can be ordered by the id field using sorted with a lambda key.

data = [
    {"id": 3, "name": "Charlie"},
    {"id": 1, "name": "Alice"},
    {"id": 2, "name": "Bob"}
]
sorted_data = sorted(data, key=lambda x: x['id'])
print(sorted_data)

[
    {"id": 1, "name": "Alice"},
    {"id": 2, "name": "Bob"},
    {"id": 3, "name": "Charlie"}
]

2. Filter elements in a list – To keep only objects that satisfy a condition (e.g., age > 18 ), use filter with a lambda.

users = [
    {"name": "Alice", "age": 22},
    {"name": "Bob", "age": 17},
    {"name": "Charlie", "age": 25}
]
adults = list(filter(lambda user: user['age'] > 18, users))
print(adults)

[{"name": "Alice", "age": 22}, {"name": "Charlie", "age": 25}]

3. Find an element in a list – Use next with a generator expression to retrieve the first matching object.

users = [
    {"name": "Alice", "age": 22},
    {"name": "Bob", "age": 17},
    {"name": "Charlie", "age": 25}
]
alice = next((user for user in users if user['name'] == 'Alice'), None)
print(alice)

{"name": "Alice", "age": 22}

4. Delete elements from a list – Re‑assign the list with a comprehension that keeps only items meeting the condition.

users = [
    {"name": "Alice", "age": 22},
    {"name": "Bob", "age": 17},
    {"name": "Charlie", "age": 25}
]
users = [user for user in users if user['age'] > 18]
print(users)

[{"name": "Alice", "age": 22}, {"name": "Charlie", "age": 25}]

5. Merge two lists – Concatenate two lists with the + operator.

list1 = ["apple", "banana"]
list2 = ["orange", "grape"]
merged_list = list1 + list2
print(merged_list)

["apple", "banana", "orange", "grape"]

6. Find the intersection of two lists – Convert both lists to set objects and use the & operator.

list1 = ["apple", "banana", "orange"]
list2 = ["orange", "grape", "banana"]
common_elements = list(set(list1) & set(list2))
print(common_elements)

["banana", "orange"]

7. Find the difference of two lists – Use set subtraction to obtain items present in the first list but not the second.

list1 = ["apple", "banana", "orange"]
list2 = ["orange", "grape", "banana"]
difference = list(set(list1) - set(list2))
print(difference)

["apple"]

8. Convert a list to a dictionary – Pair two parallel lists of keys and values with zip and feed them to dict .

keys = ["name", "age"]
values = ["Alice", 22]
dictionary = dict(zip(keys, values))
print(dictionary)

{"name": "Alice", "age": 22}

9. Use a list comprehension for filtering – A concise one‑liner that builds a new list of objects meeting a condition.

users = [
    {"name": "Alice", "age": 22},
    {"name": "Bob", "age": 17},
    {"name": "Charlie", "age": 25}
]
adults = [user for user in users if user['age'] > 18]
print(adults)

[{"name": "Alice", "age": 22}, {"name": "Charlie", "age": 25}]

10. Remove duplicate items from a list – Convert the list to a set and back to a list to obtain unique elements.

items = ["apple", "banana", "orange", "apple", "grape", "banana"]
unique_items = list(set(items))
print(unique_items)

["apple", "banana", "orange", "grape"]