Python Learning Notes (43) virtualenv (Create a set of "isolated" python runtime environments)

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When developing a Python application, the system installs only one version of the Python3:3.4. All third-party packages will be pip installed in the Python3 site-packages directory. (Linux)

If we were to develop multiple applications at the same time, those applications would share a python, which is the Python 3 installed in the system. What if application a requires Jinja 2.7 and application B needs Jinja 2.6?

In this case, each app may need to have a "standalone" Python runtime environment. Virtualenv is a python run environment that is used to create a "quarantine" for an application.

First, we use the pip installation virtualenv:

$ PIP3 Install virtualenv

Then, assuming that we are going to develop a new project, we need a separate Python runtime environment to do this:

The first step is to create the directory:

mkdir MyProject
CD MyProject

virtualenv --no-site-packages venv

' /usr/local/.../python.framework/versions/3.4 '   in venv/bin/python3.4 in venv/bin/pythoninstalling setuptools, pip, Wheel ... Done.

Command virtualenv to create a standalone Python runtime environment, we have added parameters --no-site-packages so that all third-party packages that have been installed into the system Python environment will not replicate, so that we get a "clean" without any third-party packages Python runtime environment.

The new Python environment is placed in the directory under the current directory venv . With venv This Python environment, you can source enter the environment:

Venv>scripts\activate

(venv) F:\apython_democode\cn\douzi\lesson99_virtualenv\myproject\venv>

Notice there's a venv.

Python Learning Notes (43) virtualenv (Create a set of "isolated" python runtime environments)