How to check if an element is an empty list in pandas?

You can do this:

df[df["col"].str.len() != 0]

Example:

import pandas as pd

df = pd.DataFrame({"col": [[1], [2, 3], [], [4, 5, 6], []]}, dtype=object)
print(df[df["col"].str.len() != 0])
#          col
# 0        [1]
# 1     [2, 3]
# 3  [4, 5, 6]

Try this:

df[df['col'].apply(len).gt(0)]

This is probably the most efficient solution.

df[df["col"].astype(bool)]

bool

An empty list in a boolean context is False. An empty list is what we call falsey. It does a programmer well to know what objects are falsey and truthy.

You can also slice a dataframe with a boolean list (not just a boolean series). And so, I'll use a comprehension to speed up the checking.

df[[bool(x) for x in df.col]]

Or with even less characters

df[[*map(bool, df.col)]]