A pandas dataframe is implemented as an ordered dict of columns. This means that the __getitem__ [] can not only be used to get a certain column, but __setitem ... ... <看更多>

I have a pandas DataFrame with 2 columns x and y . How do I create a new column z which is the sum of the values from the other columns? ... <看更多>

In [8]: %timeit df['B'] = df['A'].isnull()*1 517 µs ± 145 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each) In [7]: %timeit df['B'] ... ... <看更多>