How to use 'subset' of dropna() of pandas

[davidkorea]

Pandas dropna(subset=None)

• dropna(subset=None)
  • subset: Labels along other axis to consider, e.g. if you are dropping rows these would be a list of columns to include.
  • 删除某一行的时候，只有在subset指定的列中存在NaN时，执行删除此行

    >>> df = pd.DataFrame({"name": ['Alfred', 'Batman', 'Catwoman'],
    ...                    "toy": [np.nan, 'Batmobile', 'Bullwhip'],
    ...                    "born": [pd.NaT, pd.Timestamp("1940-04-25"), pd.NaT]})
    >>> df
    name        toy       born
    0    Alfred        NaN        NaT
    1    Batman  Batmobile 1940-04-25
    2  Catwoman   Bullwhip        NaT

    >>> df.dropna(subset=['name', 'born'])
    name        toy       born
    1    Batman  Batmobile 1940-04-25