find nan in numpy dataframe code example

Example 1: dataframe find nan rows

df[df.isnull().any(axis=1)]

Example 2: to detect if a data frame has nan values

> df.isnull().any().any()
True

Example 3: numpy find rows containing nan

# in each case returns array of bool
np.isnan(a).any(axis=1) # rows where any value is nan
np.isnan(a).all(axis=1) # rows where all values are nan