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3.6.1 Importing packages

We import our standard libraries at this top level.

In [1]: import numpy as np
import pandas as pd
from matplotlib.pyplot import subplots

In [2]: import statsmodels.api as sm

We will provide relevant details about the functions below as they are needed.

Besides importing whole modules, it is also possible to import only a few items from a given module.

This will help keep the namespace clean.

We will use a few specific objects from the statsmodels package which we import here.

In [3]: from statsmodels.stats.outliers_influence \
import variance_inflation_factor as VIF
from statsmodels.stats.anova import anova_lm

As one of the import statements above is quite a long line, we inserted a line break \ to ease readability.

We will also use some functions written for the labs in this book in the ISLP package.

In [4]: from ISLP import load_data
from ISLP.models import (ModelSpec as MS,
summarize,
poly)

dir()

In [5]:dir()

Out[5]:['In',
'MS',
'_',
'__',
'___',
'__builtin__',
'__builtins__',
...

'poly',
'quit',
'sm',
'summarize']

This shows you everything that Python can find at the top level.

There are certain objects like __builtins__ that contain references to built-in functions like print().

Every python object has its own notion of namespace, also accessible with dir().

This will include both the attributes of the object as well as any methods associated with it.

For instance, we see 'sum' in the listing for an array.

In [6]:A=np.array([3,5,11])
dir(A)

Out[6]:...
'strides',
'sum',
'swapaxes',
...

This indicates that the object A.sum exists.

In this case it is a method that can be used to compute the sum of the array A as can be seen by typing A.sum?.

In [7]:A.sum()

Out[7]:19

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