more informative describe()

describe.py

# Credits to answer in https://stackoverflow.com/questions/53173927/pandas-extensive-describe-include-count-the-null-values

def stats(df: pd.DataFrame) -> pd.DataFrame:
    """Like describe() but return dataframe, with datatypes and ratio of NaN values"""
    st = df.describe()
    total_n = len(df)

    st.loc["dtype"] = df.dtypes
    st.loc["n"] = total_n
    st.loc["nan_n"] = total_n - df.count()  # number of NaNs
    st.loc["nan_r"] = df.isnull().mean()    # ratio NaN/total length
                  
    return st