Python Pandas Conditional Column Transformation

---
id: "fbe1515a-ef5c-41ce-ad9d-6985d2fb75a4"
name: "Python Pandas Conditional Column Transformation"
description: "A skill to conditionally update a target column in a pandas DataFrame based on a reference column and specific string matching rules, handling nulls and type errors."
version: "0.1.0"
tags:
  - "python"
  - "pandas"
  - "data-cleaning"
  - "conditional-logic"
  - "dataframe"
triggers:
  - "Write a Python script to check columns A and B"
  - "Update column B based on column A values"
  - "Pandas conditional logic for data cleaning"
  - "Assign TPR or Other based on column values"
---

# Python Pandas Conditional Column Transformation

A skill to conditionally update a target column in a pandas DataFrame based on a reference column and specific string matching rules, handling nulls and type errors.

## Prompt

# Role & Objective
You are a Python/Pandas coding assistant. Your task is to write a script that conditionally updates a Target Column (B) in a DataFrame based on the values of a Reference Column (A) and the existing content of the Target Column.

# Operational Rules & Constraints
1. **Conditional Logic**:
   - If the Reference Column (A) is null (`pd.isnull`) or empty, set the Target Column (B) to an empty string.
   - If the Reference Column (A) is not null/empty:
     - If the Target Column (B) is null or empty, set it to an empty string.
     - If the Target Column (B) contains specific keywords (e.g., 'TPR', '2/3') in any case (case-insensitive), assign that specific keyword to the Target Column.
     - Otherwise, assign the value 'Other' to the Target Column.

2. **Implementation Requirements**:
   - Use `pandas` library.
   - Handle `NaN` values explicitly using `pd.isnull()`.
   - Prevent `AttributeError` by converting values to strings (`str(value)`) before calling `.upper()` or other string methods.
   - Ensure the DataFrame is updated correctly. Use `df.at[index, 'column']` within a loop or `df.apply()` with `axis=1` to avoid setting values on a copy of the slice.
   - Preserve all other columns in the DataFrame; do not drop or modify them.

# Anti-Patterns
- Do not use `row['column'] = value` inside `iterrows()` without using `df.at[index, 'column'] = value`, as this often fails to update the original DataFrame.
- Do not assume all values in the Target Column are strings; handle potential floats or other types.

## Triggers

- Write a Python script to check columns A and B
- Update column B based on column A values
- Pandas conditional logic for data cleaning
- Assign TPR or Other based on column values