Explain Codes LogoExplain Codes Logo

How to select rows with one or more nulls from a pandas DataFrame without listing columns explicitly?

python
dataframe
null-values
data-cleaning
Alex KataevbyAlex Kataev·Feb 21, 2025
TLDR

To swiftly find rows with at least one missing value in a DataFrame, we can deploy df[df.isna().any(1)]. This operation systematically sifts in those rows that have any nulls across all their columns.

import pandas as pd # Assuming 'df' is your DataFrame # Much like hiring for a job, we're interested # only in rows that have no blanks in their bio! filtered_df = df[df.isna().any(axis=1)]

filtered_df will constitute only those rows that are plagued with at least one NaN.

One-liner solutions

Drill-down with null count

To target rows with a precise count of nulls and the drill-down to those rows with a specific count of nulls, there's your trusty line df.isnull().sum(axis=1) along with a logical condition to allow a more granular, sharp filter.

# Anyone got exactly two NaN values? Show of hands, please! df[df.isnull().sum(axis=1) == 2]

Scalability is key

When dealing with heavyweight DataFrames, avoid loops like you avoid last day's leftover salad. The isna().any() approach is your shield and sword offering scalability while staying efficient.

Code readability

Who else hates deciphering code like it's a 2000-year-old relic script? The methods here are transparent, readable, and maintainable, that even novices navigate without a hiccup.

Fine-tuning selection

Null management

Some days, you want to find nulls, and on others, you manipulate DataFrames accordingly. Here's a cool trick to create an exclusive club — a new DataFrame for rows with nulls:

# If you have NaN, this is your VIP lounge! null_rows_df = df[df.isnull().any(axis=1)]

Steer clear of deprecated methods

With ever-evolving pandas, it's essential to stay relevant. Embrace .iloc and canned methods like ix. Bonus: no annoying deprecation warnings.

Setting stage for analysis

Having the null rows separate renders data cleaning or analysis a breeze. Whether it's planning for imputation or deletion, segregating makes it all smooth.

Scope matters

While it's tempting to drop rows and reset indices, the goal is to find a solution that stays within bounds. Visibility on core requirement helps craft focussed solutions.