How to Get Length of a List in Python

What you’ll build or solve

You’ll get the number of items in a Python list and use that number in real code.

When this approach works best

Getting the length of a list works well when you:

• Validate input, like checking a list of results before accessing items[0].
• Control loops, like stopping after N items or chunking data into batches.
• Compare lists, like confirming two lists have the same number of items before pairing them.

Skip this approach if you only need to loop over items. A for item in items loop doesn’t need the length and is usually easier to read.

Prerequisites

• Python 3 installed
• You know what a list is

Step-by-step instructions

1) Get the length with len()

Use len() to get the number of items in a list.

nums = [10, 25, 30]
count = len(nums)

print(count)

What to look for: len([]) returns 0, so empty lists won’t crash your code.

2) Use the length to check for an empty list

A quick length check helps you avoid IndexError when accessing elements.

Option A (most common): Use the list directly in a condition

items = []

if items:
    first = items[0]
else:
    first = None

print(first)

Option B: Compare len() to 0 for clarity

items = []

if len(items) > 0:
    first = items[0]
else:
    first = None

print(first)

What to look for: if items: is the standard Python pattern. Empty lists are treated as False.

3) Use the length safely with indexes

Valid indexes stop at len(items) - 1.

names = ["Amina", "Luka", "Noor"]

last_index = len(names) - 1
last_name = names[last_index]

print(last_name)

What to look for: If the list might be empty, len(names) - 1 becomes -1. That’s a valid index in Python, but it means “last item,” so check for emptiness first when that matters.

Examples you can copy

Example 1: Guard before accessing the first item

results = ["match_1", "match_2"]

if results:
    print("First result:", results[0])
else:
    print("No results")

Example 2: Take the last N items (or fewer)

items = ["a", "b", "c", "d", "e"]
n = 3

start = max(len(items) - n, 0)
tail = items[start:]

print(tail)

Example 3: Process a list in batches of size N

items = list(range(10))
batch_size = 4

for start in range(0, len(items), batch_size):
    batch = items[start:start + batch_size]
    print(batch)

Example 4: Check two lists have the same length before zipping

names = ["Amina", "Luka", "Noor"]
scores = [42, 38, 50]

if len(names) != len(scores):
    raise ValueError("Lists must have the same length")

pairs = list(zip(names, scores))
print(pairs)

Example 5: Count items that match a condition

len() counts all items in a list, not items that match a rule. Filter first, then measure.

scores = [10, 0, 25, 30]
non_zero_count = len([s for s in scores if s != 0])

print(non_zero_count)

Common mistakes and how to fix them

Mistake 1: Off-by-one indexing

What you might do:

names = ["Amina", "Luka", "Noor"]
last = names[len(names)]

Why it breaks: Valid indexes stop at len(names) - 1, so len(names) is out of range.

Correct approach:

names = ["Amina", "Luka", "Noor"]
last = names[len(names) - 1]

print(last)

Or use negative indexing:

names = ["Amina", "Luka", "Noor"]
last = names[-1]

print(last)

Mistake 2: Using length checks where you don’t need them

What you might do:

items = ["a", "b", "c"]

for i in range(len(items)):
    print(items[i])

Why it breaks: Nothing crashes, but the code is harder to read and easier to mess up than a direct loop.

Correct approach:

items = ["a", "b", "c"]

for item in items:
    print(item)

Mistake 3: Assuming len() tells you how many items match a rule

What you might do:

scores = [10, 0, 25, 30]
count = len(scores != 0)

Why it breaks: scores != 0 does not filter the list and does not return something you can measure.

Correct approach:

scores = [10, 0, 25, 30]
count = len([s for s in scores if s != 0])

print(count)

Troubleshooting

If you see TypeError: object of type ... has no len(), the variable isn’t a list or another sized container. Print type(x) to confirm what you’re working with.

If you see IndexError: list index out of range, you likely used len(items) instead of len(items) - 1.

If your code returns an unexpected result for the last item, check for empty lists and watch out for -1 indexing.

If your loop feels complicated, try for item in items and avoid indexes unless you truly need them.

Quick recap

• Use len(my_list) to get the number of items.
• len([]) is 0, so empty lists are safe to measure.
• Valid indexes stop at len(my_list) - 1.
• Use if my_list: to check for emptiness.
• Filter first if you want the count of items that match a condition.