Using conda

Overview

Teaching: 15 min
Exercises: 3 min

Questions

• How can I use conda to create new environments?

• How can I use conda to install packages?

• Why should I use python environments during development?

Objectives

• Understand how to create and activate environments with conda

Using Anaconda and conda

Use of Anaconda with its package manager, conda, greatly simplifies package installation and environment management.

conda is a general package manager, meaning that it can install dependencies and packages in languages besides Python, unlike pip (which is Python’s package manager). Both pip and conda can be used to install packages.

Python environments

A conda environment contains a specific collection of packages you have installed. This means that packages are isolated, and installed only for a specific environment – you can have several environments each with different installed packages, or different versions of installed packages in different environments.

It’s considered a best practice to create a new Python environment for each project you work on.

To create an environment for this project using conda,

$ conda create --name sss_2019 python=3.7

For other projects, you should replace sss_2019 with a descriptive name for your project. conda also allows you to specify the python version to use with the environment. Here, python=3.7 specifies that we want to use Python 3.7 in this environment. Executing this command will list the environment location and a list of Python packages to be installed. Choose y(es) when prompted.

Activate the environment using the command

$ conda activate sss_2019

Once you’ve activated an environment, the name of the environment will be in parenthesis at the front of your command line prompt.

If you wanted to create an environment for testing your code in Python 2.7, for example, you could use the command

$ conda create --name sss_2019-27 python=2.7

When this environment is activated, Python 2.7 will be used instead of Python 3.7.

To see a list of all your environments

$ conda info --envs

To deactivate an environment, type

$ conda deactivate

Check your understanding

How can you activate the environment sss_2019. How can you tell that you’re using the environment?

Answer

You activate the environment using the command

$ conda activate sss_2019

You can tell you are in the environment because it will appear at the beginning of your command prompt.

Package installation using conda

Using conda, we can install packages to our environments. Note: Make sure you have activated the environment where you want to install packages.

To list all the Python packages installed in an environment, first activate it, then type

$ conda list

Packages can be installed using the conda install package_name command. For example, to install NumPy,

$ conda install numpy

Further, the desired version of NumPy can be specified:

$ conda install numpy=1.15

Key Points

• conda is a package manager that can be used to create environments and install packages.