Reference library

Lists & loops

Iterate, transform, and combine sequences with readable loop patterns.

1 match
Lists & loops easy

How to Filter a List in Python with a Loop

Filter a list of numbers by a threshold using a for loop and append results to a new list, then print the filtered values and count.

filter for-loop lists
Python 
ages = [34, 12, 45, 8, 67, 21, 18, 55, 3]
threshold = 18

adults = []
for age in ages:
    if age >= threshold:
        adults.append(age)

print("All ages:", ages)
print("Adults (18+):", adults)
print("Count of adults:", len(adults))
10 0 Open

Browse by section

Each section groups closely related Python snippets.

Lists & loops — Python code examples

What you will find here

This page collects lists & loops snippets — short, copy-ready Python you can paste into our free online IDE and run without installing anything. Each sample includes a plain-English explanation and the full source code.

Samples vs tutorials and challenges

Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.

Related coding tools

Free online Python IDE Write and run Python in your browser — no install. Free Python code formatter Format with autopep8 — side-by-side PEP 8 cleanup. Python code samples Copy-ready snippets to study and run in the IDE.