Creating and Managing Python environments with Conda

Conda is the package manager for Anaconda Python distribution.In this article we will explore following topics.

• What Python environments are.
• Why and when we need Python environments.
• How to create and manage Python environments using conda.

Please follow the official documentation to install conda.

What Is Python Virtual Environment and why we need it?

Virtual environment helps to create a sandbox by isolating dependencies required by a specific python project. As a result each python project can have an isolated environment / sandbox with it’s own dependencies, regardless of the decencies a-viable elsewhere on the same system.

Why Use Virtual Environment?

In this section I will list some of reasons and benefits of creating and managing multiple virtual environments for Python development.

1. Major operating systems like macOS come with pre-installed version of Python, however the version installed with OS might be an older one and in some cases upgrading this default installation my compromise the proper working on system components.
2. With default global installation using pip, it’s not possible to install different packages with
3. Virtual environment enables you to use different version of a same package for different projects.
4. By default pip installs the python packages globally, this may result in conflicts. same name. However virtual environment makes it easy to install packages within the project sandbox.

Creating a virtual environment with conda

Open a terminal / command prompt and run following command to create a new virtual environment.

conda create --name newenv

On execution of above command, conda will ask you to proceed, type y to proceed with creation of virtual environment.

proceed ([y]/n)?

Creating a virtual environment with Python package

You can also specify a Python package during the creation of a virtual environment using following command.

conda create -n newenv numpy

Above command will install numpy package in newenv virtual environment, in other words the package numpy installed through above command will only be available within the sandbox of newenv virtual environment.

You can install a specific version of a python package as following

conda install --name newenv numpy=1.16.4

Use following command to install specific versions of multiple packages with creation of a new virtual environment.

conda create -n newenv urlopen=1.0.0 numpy=1.16.4 PyFEBOL=0.3.3

Creating a virtual environment with Python version

During creation of a virtual environment, we can also specify a particular version of Python as following.

conda create -n newenv python=3.4

Use following command to create a new virtual environment with a specific python version and multiple packages.

conda create -n newenv python=3.4 urlopen=1.0.0 numpy=1.16.4 PyFEBOL=0.3.3

Activating a virtual environment

Following tasks are performed when we activate a virtual environment.

1. Environment specific entries are added in PATH.
2. Any activation scripts specified for this environment are executed.

Run following command to activate a specific environment, please replace the newenv with your environment name.

conda activate newenv

Deactivating a virtual environment

Run following command to deactivate currently active virtual environment, in context of this article following command will deactivate environment named newenv.

conda deactivate

Listing available virtual environments

You can execute following command to list available virtual environments on your system.

conda env list

Output of conda env list command.

# conda environments:
#
untitled                 /Users/sma/.conda/envs/untitled
newenv                *  /Users/sma/.conda/envs/newenv
base                     /anaconda3

The symbol * indicates the currently active environment.

Alternatively you can run conda info command as following to print a list of available virtual environments on your system.

conda info --envs

Output of conda info --envs command.

# conda environments:
#
untitled                 /Users/sma/.conda/envs/untitled
newenv                *  /Users/sma/.conda/envs/newenv
base                     /anaconda3

Using pip in a conda virtual environment

You can easily use pip package manager from within the virtual environment created using conda, let’s explore the details.

1. Before you can use pip, you need to install it within your virtual environment using conda install command. Following command will create a virtual environment named newenv and install pip in it. conda install -n newenv pip
2. Activate the newly created environment. conda activate newenv
3. Now you are ready to use pip in your conda virtual environment, in following example replace the pip_command with proper pip subcommand. pip pip_command

Removing a conda virtual environment

You can use following command to remove a conda virtual environment from your system, please replace the name newenv with the name of environment that you want to remove from your system.

conda remove --name newenv

Run the conda env list command to verify the removal of virtual environment named newenv.

conda env list

Following output confirms that the environment namednewenv is no longer available on our system.

# conda environments:
#
untitled                 /Users/sma/.conda/envs/untitled
base                   * /anaconda3

Creating a virtual environment with environment.yml file

You can create conda virtual environment YAML file (environment.yml) instead of terminal commands, in this section we explore the process of virtual environment ceration using environment.yml file.

Following listing show basic structure of a environment.yml file.

name: name_of_virtual_enviornment
channels:
  - ...
dependencies:
  - ...

Following is a sample environment.yml file.

name: testenv
channels:
  - javascript
dependencies:
  - python=3.4
  - numpy=1.16.4
  - urlopen=1.0.0
  - PyFEBOL=0.3.3
  - flask
  - pip:
    - Flask-Testing

Save the above file as environment.yml in your project directory, and fun following command to create a new virtual environment using this file.

conda env create -f environment.yml

One of the core advantages of using environment.yml file is that you can easily share this environment with your team members and friends.

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This article is part of Python Programming, IoT, Big Data, Data Science, AI and Machine Learning Tutorials Series, please click here to visit the complete list of articles and tutorials in this series.

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Thanks and Happy Learning!