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List Methods · Examples
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List Methods Examples

Short, runnable programs that show python list methods in action. Read the explanation, press Run, then change the code and try your own ideas. New to the topic? Start with the Python List Methods lesson.

1append, extend or +: three ways to combine lists

Adding one list to another gives three different results. append() nests it, extend() merges it in place, and + makes a new list.

append, extend or +: three ways to combine lists 
morning = ["email", "standup"]
afternoon = ["review", "deploy"]

as_one_item = morning.copy()
as_one_item.append(afternoon)
print(as_one_item)

merged = morning.copy()
merged.extend(afternoon)
print(merged)

combined = morning + afternoon
print(combined)
print(morning)
Expected output['email', 'standup', ['review', 'deploy']]
['email', 'standup', 'review', 'deploy']
['email', 'standup', 'review', 'deploy']
['email', 'standup']

2A browser history as a stack

A stack is last-in, first-out. append() pushes a page and pop() takes the newest one back off, like the Back button.

A browser history as a stack 
history = ["home"]
for page in ["search", "product", "cart"]:
    history.append(page)
    print("Visited", page, "->", history)

while len(history) > 1:
    leaving = history.pop()
    print("Back from", leaving, "to", history[-1])
Expected outputVisited search -> ['home', 'search']
Visited product -> ['home', 'search', 'product']
Visited cart -> ['home', 'search', 'product', 'cart']
Back from cart to product
Back from product to search
Back from search to home

3A print queue served from the front

A queue is first-in, first-out, so jobs are taken from position 0. The loop runs while the list is not empty (an empty list counts as false).

A print queue served from the front 
jobs = ["report.pdf", "photo.png", "notes.txt"]
while jobs:
    current = jobs.pop(0)
    print("Printing", current, "-", len(jobs), "left")
print("Queue empty:", jobs)
Expected outputPrinting report.pdf - 2 left
Printing photo.png - 1 left
Printing notes.txt - 0 left
Queue empty: []

4remove() deletes only the first match

When a value appears several times, one remove() takes out one copy. Loop with in to clear them all.

remove() deletes only the first match 
tags = ["sale", "new", "sale", "sale", "hot"]
print("sale appears", tags.count("sale"), "times")
tags.remove("sale")
print(tags)
while "sale" in tags:
    tags.remove("sale")
print(tags)
Expected outputsale appears 3 times
['new', 'sale', 'sale', 'hot']
['new', 'hot']

5Finding positions with index() and count()

index() accepts a second argument, the position to start searching from. That lets you find the second match, and the third, and so on.

Finding positions with index() and count() 
levels = ["INFO", "ERROR", "INFO", "WARN", "ERROR", "INFO"]
print("errors:", levels.count("ERROR"))
first = levels.index("ERROR")
second = levels.index("ERROR", first + 1)
print("first error at", first, "second at", second)
print("no CRITICAL:", levels.count("CRITICAL") == 0)
Expected outputerrors: 2
first error at 1 second at 4
no CRITICAL: True

6Edit a copy and keep the original

copy() gives you a separate list, so you can experiment with reverse(), insert() and pop() while the original stays exactly as it was.

Edit a copy and keep the original 
original = ["red", "green", "blue"]
draft = original.copy()
draft.reverse()
draft.insert(1, "yellow")
draft.pop()
print("original:", original)
print("draft:", draft)
Expected outputoriginal: ['red', 'green', 'blue']
draft: ['blue', 'yellow', 'green']

Practise next

Python List Methods exercises → Back to the lesson

Python Lists examplesPython Slicing examplesPython Tuples examplesPython Sorting examples