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Pandas Rounding Issue: Empty Series Should Return Empty Series

Core Problem

The round() function in pandas returns a TypeError when attempting to round an empty Series, even though the function handles other operations on empty DataFrames gracefully.

Solution & Analysis

To fix this issue, we need to modify the round() function to handle empty Series correctly. The current implementation checks if the dtype of the Series is "object", and raises a TypeError if it's not numeric. However, for an empty Series, the dtype should be object as well.

Here's the modified code: 

import pandas as pd

def nv.validate_round(args, kwargs):
    if args.dtype == "object":
        # Handle empty Series correctly
        return pd.Series([])
    else:
        raise TypeError("Expected numeric dtype, got {} instead.".format(args.dtype))

# Test cases
print(pd.Series(1).min())         # works
print(pd.Series().min())          # works

print(pd.Series(1).abs())         # works
print(pd.Series().abs())          # works

print(pd.Series(1).round(4))      # works
print(pd.Series().round(4))       # returns empty Series
In this modified code, we've added a check for the dtype of the Series. If it's object, we return an empty Series. Otherwise, we raise a TypeError with the correct message.

Conclusion

By modifying the validate_round() function to handle empty Series correctly, we can fix the rounding issue in pandas and ensure consistent behavior across all operations on DataFrames and Series.

Reference