convert object data to categorical data code example

Example 1: using df.astype to select categorical data and numerical data

df = pd.DataFrame({'vertebrates': ['Bird', 'Bird', 'Mammal', 'Fish', 'Amphibian', 'Reptile', 'Mammal']})

df.vertebrates.astype("category").cat.codes

Example 2: pandas difference between object and category

In [6]: %timeit trades.groupby('exch')['size'].sum()
1000 loops, best of 3: 1.25 ms per loop