How do I check if a list is empty in Python?

Short answer

Write if not items:. Empty collections are falsy in Python, so this reads better and works identically for lists, dicts, sets, tuples and strings.

python

items = []

if not items:
    print("nothing here")

#What is falsy in Python

Everything else is truthy. That includes "0", "False" and [0] — all non-empty, therefore true.

python

if len(items) == 0:      # works, but wordier
if items == []:          # works, but only for lists
if not items:            # idiomatic

The idiomatic form is what other Python developers expect, and it works unchanged if items later becomes a set or a tuple.

It does not distinguish empty from None

if not items is true for both [] and None. When that difference matters — "no data" versus "not loaded yet" — check explicitly:

python

if items is None:
    load()
elif not items:
    print("loaded, but empty")

python

if items:
    print(f"{len(items)} items")

NumPy arrays raise ValueError on truth testing, because the answer is ambiguous for more than one element. Use array.size == 0 there.