Getting error message when using 'np.where'

Question

I have defined a function that should add a new column called season to the data frame. The values of season are extracted from the date column:

def season(df):

    df['sum'] = ((df['date'].dt.month) * 100) + df['date'].dt.day

    df['season'] = np.where(df['sum'] > 320 & df['sum'] < 621, 1, np.where(df['sum'] > 620 & df['sum'] < 923, 2, np.where(df['sum'] > 922 & df['sum'] < 1223, 3, 4)))

    df.drop(['sum'], axis=1, inplace=True)

    return df

But when I call this function inside the main code, I get this error message: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Where should be modified?

Thanks.

Quang Hoang · Accepted Answer · 2020-03-02 03:44:10Z

1

Put df['sum'] >320 inside brackets, i.e. (df['sum']>320)&(...).

Or you can use gt and lt: df['sum'].gt(320)

answered Mar 2, 2020 at 3:44

Quang Hoang

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