Source: View original notebook on GitHub

Category: Python / 1 Learn Python

Virtual Environments and Packages

• use pip list to see which packages are installed in our directory.

• First up globally use pip install virtualenv to install virtualenv package.

• Now to create a virtual env in our desired folder use virtualenv project1_env to make a folder project1_env as our python virtual environment.(this will install setuptools,pip,wheel in project1_env to create a virtual environment for us)

• next step is to activate this env type project1_env\Scripts\activate.bat note the backward slashes\

• to come out of your virtual environnment just type deactivate

Introduction

• Python applications will often use packages and modules that don’t come as part of the standard library. Applications will sometimes need a specific version of a library, because the application may require that a particular bug has been fixed or the application may be written using an obsolete version of the library’s interface.

• This means it may not be possible for one Python installation to meet the requirements of every application. If application A needs version 1.0 of a particular module but application B needs version 2.0, then the requirements are in conflict and installing either version 1.0 or 2.0 will leave one application unable to run.

• The solution for this problem is to create a virtual environment, a self-contained directory tree that contains a Python installation for a particular version of Python, plus a number of additional packages.

• Different applications can then use different virtual environments. To resolve the earlier example of conflicting requirements, application A can have its own virtual environment with version 1.0 installed while application B has another virtual environment with version 2.0. If application B requires a library be upgraded to version 3.0, this will not affect application A’s environment.