什么是虚拟环境？ (What is Virtual Environment?)

Virtual environments are very useful when the application requires a separate environment, each using its version of python and libraries for execution. Similar to virtual environment, there are packaging tools like "Anaconda" and "Miniconda".

当应用程序需要单独的环境时， 虚拟环境非常有用，每个环境都使用其python版本和库来执行。 与虚拟环境类似，有打包工具，例如“ Anaconda”和“ Miniconda” 。

The virtual environment is the easiest and recommended way to configure a custom python environment.

虚拟环境是配置自定义python环境的最简单且推荐的方法。

为什么我们需要一个虚拟环境？ (Why do we need a virtual environment?)

The virtual environment is a clever way to keep the python setup isolated with other projects. As a user, one can have multiple virtual environments in a single machine and each virtual environment can have different libraries as per the requirements. We can also package a virtual environment like a zip file with all dependencies needed for the application and deploy it on serverless service like AWS lambda.

虚拟环境是一种使python安装程序与其他项目隔离的聪明方法。 作为用户，可以在一台计算机上拥有多个虚拟环境，并且每个虚拟环境可以根据要求具有不同的库。 我们还可以将虚拟环境(如zip文件)打包为应用程序所需的所有依赖项，并将其部署在AWS lambda等无服务器服务上。

如何使用Python3创建虚拟环境？ (How to create a virtual environment using Python3?)

Step1: Install Virtual Environment

步骤1：安装虚拟环境

pip3 install virtualenv
Collecting virtualenv
Downloading virtualenv-15.1.0-py2.py3-none-any.whl (1.8MB)
100% |████████████████████████████████| 1.8MB 367kB/s
Installing collected packages: virtualenv
Successfully installed virtualenv-15.1.0

Step2: Using python3, the command to create the virtual environment and the syntax is 'python3 –m venv /path/to/create/the/virtual/env'.

步骤2：使用python3创建虚拟环境的命令和语法为'python3 –m venv / path / to / create / the / virtual / env' 。

-bash-4.2$ python3 -m venv test_venv
-bash-4.2$ ls
test_venv
-bash-4.2$

Step3: Activate virtual environment

第三步：激活虚拟环境

-bash-4.2$ source test_venv/bin/activate
(test_venv) -bash-4.2$

Step4: Install the required libraries, using pip (for the example below, we have used 'flask' library)

第4步：使用pip安装所需的库(对于以下示例，我们使用了“ flask”库)

(test_venv) -bash-4.2$ pip3 install flask
Collecting flask
Downloading https://files.pythonhosted.org/packages/9b/93/628509b8d5dc749656a9641f4caf13540e2cdec85276964ff8f43bbb1d3b/Flask-1.1.1-py2.py3-none-any.whl (94kB)
100% |████████████████████████████████| 102kB 3.8MB/s
Collecting Jinja2>=2.10.1 (from flask)
Using cached https://files.pythonhosted.org/packages/1d/e7/fd8b501e7a6dfe492a433deb7b9d833d39ca74916fa8bc63dd1a4947a671/Jinja2-2.10.1-py2.py3-none-any.whl
Collecting click>=5.1 (from flask)
Using cached https://files.pythonhosted.org/packages/fa/37/45185cb5abbc30d7257104c434fe0b07e5a195a6847506c074527aa599ec/Click-7.0-py2.py3-none-any.whl
Collecting itsdangerous>=0.24 (from flask)
Using cached https://files.pythonhosted.org/packages/76/ae/44b03b253d6fade317f32c24d100b3b35c2239807046a4c953c7b89fa49e/itsdangerous-1.1.0-py2.py3-none-any.whl
Collecting Werkzeug>=0.15 (from flask)
Using cached https://files.pythonhosted.org/packages/ce/42/3aeda98f96e85fd26180534d36570e4d18108d62ae36f87694b476b83d6f/Werkzeug-0.16.0-py2.py3-none-any.whl
Collecting MarkupSafe>=0.23 (from Jinja2>=2.10.1->flask)
Using cached https://files.pythonhosted.org/packages/b2/5f/23e0023be6bb885d00ffbefad2942bc51a620328ee910f64abe5a8d18dd1/MarkupSafe-1.1.1-cp36-cp36m-manylinux1_x86_64.whl
Installing collected packages: MarkupSafe, Jinja2, click, itsdangerous, Werkzeug, flask
Successfully installed Jinja2-2.10.1 MarkupSafe-1.1.1 Werkzeug-0.16.0 click-7.0 flask-1.1.1 itsdangerous-1.1.0
(test_venv) -bash-4.2$

翻译自: https://www.includehelp.com/python/virtual-environment-for-python-based-application.aspx