Pandas Debugging Guide

A systematic approach to debugging Pandas DataFrames and operations using the OILER framework (Orient, Investigate, Locate, Experiment, Reflect).

Common Error Patterns

1. SettingWithCopyWarning

Symptom: Warning message about setting values on a copy of a slice.

Cause: Modifying a view of a DataFrame rather than a copy. Pandas cannot guarantee whether the operation affects the original data.

Solution:

# BAD - triggers warning
df_subset = df[df['col'] > 5]
df_subset['new_col'] = 10  # Warning!