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How to implement guide with dataframe.apply() not applying function correctly when passing axis=1 with mixed data types

๐Ÿ‘€ Views: 30 ๐Ÿ’ฌ Answers: 1 ๐Ÿ“… Created: 2025-06-10
pandas dataframe apply axis Python

I can't seem to get I've searched everywhere and can't find a clear answer. I'm deploying to production and I'm working with an scenario when trying to use `DataFrame.apply()` on a DataFrame that contains mixed data types (integers, floats, and strings). I want to apply a custom function to each row that calculates a weighted score based on certain conditions. However, I'm getting unexpected results when passing `axis=1`. Hereโ€™s what I have: ```python import pandas as pd data = { 'A': [1, 2, 3], 'B': [4.5, 5.5, 6.5], 'C': ['low', 'medium', 'high'] } df = pd.DataFrame(data) # Custom function to calculate score def calculate_score(row): score = row['A'] * 2 # A simple calculation based on column 'A' if row['C'] == 'high': score += 10 elif row['C'] == 'medium': score += 5 return score result = df.apply(calculate_score, axis=1) print(result) ``` The output I expected was: ``` 0 12 1 10 2 16 dtype: int64 ``` but instead, Iโ€™m getting: ``` 0 12.0 1 10.0 2 NaN dtype: float64 ``` Iโ€™ve double-checked my function and it seems correct. I even tried explicitly converting the values in the function, but that didnโ€™t help. Iโ€™m using Pandas version 1.3.0. Could this be related to how Pandas handles mixed data types, or is there something I'm missing in the function logic? Am I approaching this the right way? Am I missing something obvious? This issue appeared after updating to Python latest.