Regression: to_csv and multiindex columns with header kw · Issue #5539 · pandas-dev/pandas (original) (raw)

from pandas import DataFrame import numpy as np import StringIO a = ["a","b","a","b","a","b","a","b","a","b","a","b"] b = ["c","d","e","c","d","e","c","d","e","c","d","e"] c = [1,2,3,4,5,6,7,8,9,10,11,12] d = list(reversed(c)) df = DataFrame({"a":a, "b":b, "c":c, "d":d}) agg_funs = [np.mean, np.std, np.min, np.max] groupby_variables = ["a","b"] df_grouped = df.groupby(groupby_variables, as_index=True).agg(agg_funs) output = StringIO.StringIO() df_grouped.to_csv(output, header=[var + "" + agg for (var, agg) in df_grouped.columns]) index = output.getvalue().split("\n")[0].split(",") expected_index = groupby_variables + [var + "" + agg for (var, agg) in df_grouped.columns] print(index == expected_index) # This was true in October 2012! print(index) print(expected_index)

False ['', '', 'c', 'c', 'c', 'c', 'd', 'd', 'd', 'd'] ['a', 'b', 'c_mean', 'c_std', 'c_amin', 'c_amax', 'd_mean', 'd_std', 'd_amin', 'd_amax']