[英]Pandas agg function different behaviours depending on call definition
I don't understand the agg
behaviour. 我不了解agg
行为。 See examples below and expected result. 请参阅以下示例和预期结果。
pd.DataFrame({'d': [{'a': 1}, {'b': 2}]}).agg(list)
Out[372]:
d
0 {'a': 1}
1 {'b': 2}
pd.DataFrame({'d': [{'a': 1}, {'b': 2}]}).agg(lambda col: list(col))
Out[373]:
d
0 {'a': 1}
1 {'b': 2}
pd.DataFrame({'d': [{'a': 1}, {'b': 2}]}).agg({'d': list})
Out[374]:
d
0 [a]
1 [b]
pd.DataFrame({'d': [{'a': 1}, {'b': 2}]}).agg({'d': lambda col: list(col)})
Out[375]:
d
0 [a]
1 [b]
Expected result is: 预期结果是:
pd.DataFrame({'d': [list(pd.DataFrame({'d': [{'a': 1}, {'b': 2}]}).d)]})
Out[379]:
d
0 [{'a': 1}, {'b': 2}]
You might need another DataFrame
: 您可能需要另一个DataFrame
:
>>> df = pd.DataFrame({'d': [{'a': 1}, {'b': 2}]})
>>> pd.DataFrame([df.values], columns=df.columns)
d
0 [[{'a': 1}], [{'b': 2}]]
>>>
agg
isn't able to do that, it aggregates and does X operation on Y column, it doesn't "aggregate" values... agg
无法做到这一点,它会聚合并对Y列执行X操作,它不会“聚合”值...
For your other example, I would do: 对于另一个示例,我将这样做:
>>> pd.DataFrame(df.apply(lambda x: [df[x.name].values])).T.apply(lambda x: x.str[0])
d e
0 [{'a': 1}, {'b': 2}] [{'a': 1}, {'b': 2}]
>>>
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