Lesson 8 - Python Ecosystem

Don’t reinvent the wheel.

Learning objectives

Importing packages
Installing packages with pip
Introduction to conda

Lecture material

(<45 minutes)

Libraries

A python library is a collection of functions and methods that allows you to perform many actions without writing your own code.

We have already encountered and learned to use some of the popular libraries: numpy, pandas, matplotlib, and seaborn.

Many libraries come installed with anaconda including both pandas and seaborn. However, these libraries are not imported when you open a jupyter notebook, so we have to tell python which libraries we would like to use.

Importing Libraries

The most basic way to import a libary is to use import. The syntax of importing a library is like

import library_name

We can also use as to give an alias.

import library_name as alias

Now the library can be accessed using the alias. We have already used this approach when importing libraries like pandas, numpy, matplotlib, and seaborn.

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

---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
Cell In[1], line 3
      1 import numpy as np
      2 import pandas as pd
----> 3 import seaborn as sns

ModuleNotFoundError: No module named 'seaborn'

In the previous lectures we have used pandas data frames. When using a module within a library we use it after the library name and a dot. For example, pd.DataFrame or np.array.

What if we want to use only the specific functions/classes within a module? In that case, we can use from library import function. For example, we want to use the permutation function from numpy.

In that case we can do

from numpy.random import permutation

Now we can use the permutation function like we use other functions.

permutation(list(range(10)))

array([6, 8, 0, 9, 1, 3, 5, 4, 7, 2])

Hopefully, you can see how importing data from and exporting data to csv or other delimiter separated files will be helpful for research. Now it’s time to practice your skills with built-in data structures and data frames!

Python ecosystem

One reason why python is such a powerful language is because of the python ecosystem (especially for data science).

drawing

Installing libaries

Now, what if we want to use a new library? In this part, we will learn how to install new libraries. In python, there are package managers like pip and conda that will make your life easier when installing and removing python libraries. You can go to your terminal and type in:

where pip3

to ensure you have pip3 (pip for Python 2) on your machine.

The standard way of installing library with pip is:

python3 -m pip install "library name"

Another awesome and popular package manager is Anaconda. Anaconda can be easily installed on to your local machine (windows, linux, and mac) from their website.