NB: Method Chaining

Method chaining is supported by many objects in Python.

This allows you to “chain” a series of methods without having to defined temporary variables.

import numpy as np
import pandas as pd
import seaborn as sns

iris = sns.load_dataset('iris')

iris

	sepal_length	sepal_width	petal_length	petal_width	species
0	5.1	3.5	1.4	0.2	setosa
1	4.9	3.0	1.4	0.2	setosa
2	4.7	3.2	1.3	0.2	setosa
3	4.6	3.1	1.5	0.2	setosa
4	5.0	3.6	1.4	0.2	setosa
...	...	...	...	...	...
145	6.7	3.0	5.2	2.3	virginica
146	6.3	2.5	5.0	1.9	virginica
147	6.5	3.0	5.2	2.0	virginica
148	6.2	3.4	5.4	2.3	virginica
149	5.9	3.0	5.1	1.8	virginica

150 rows × 5 columns

iris.index.name = 'iris_id'

iris

	sepal_length	sepal_width	petal_length	petal_width	species
iris_id
0	5.1	3.5	1.4	0.2	setosa
1	4.9	3.0	1.4	0.2	setosa
2	4.7	3.2	1.3	0.2	setosa
3	4.6	3.1	1.5	0.2	setosa
4	5.0	3.6	1.4	0.2	setosa
...	...	...	...	...	...
145	6.7	3.0	5.2	2.3	virginica
146	6.3	2.5	5.0	1.9	virginica
147	6.5	3.0	5.2	2.0	virginica
148	6.2	3.4	5.4	2.3	virginica
149	5.9	3.0	5.1	1.8	virginica

150 rows × 5 columns

iris = iris.reset_index()\
    .set_index(['species', 'iris_id'])

iris

		level_0	index	sepal_length	sepal_width	petal_length	petal_width
species	iris_id
setosa	0	0	0	5.1	3.5	1.4	0.2
	1	1	1	4.9	3.0	1.4	0.2
	2	2	2	4.7	3.2	1.3	0.2
	3	3	3	4.6	3.1	1.5	0.2
	4	4	4	5.0	3.6	1.4	0.2
...	...	...	...	...	...	...	...
virginica	145	145	145	6.7	3.0	5.2	2.3
	146	146	146	6.3	2.5	5.0	1.9
	147	147	147	6.5	3.0	5.2	2.0
	148	148	148	6.2	3.4	5.4	2.3
	149	149	149	5.9	3.0	5.1	1.8

150 rows × 6 columns

iris.groupby('species').mean('mean').plot.barh();

iris.groupby('species').agg('mean').T.setosa.plot.barh();

iris.groupby(['sepal_length','sepal_width']).petal_length\
    .mean()\
    .to_frame('mean petal_length')\
    .plot(style='.', rot=45);