Elegant python Environment Management and python Environment Management

Elegant python Environment Management and python Environment Management

Elegant python Environment Management

Origin

Scenario 1: manage different python versions

For the management of multiple python versions on the same computer, in order to highlight the common problems, the following are some questions raised on segmentfault.

From: http://segmentfault.com/q/1010000000162043

Scenario 2: manage different versions of the same library in the same python version

For example, in python2.7, application A is based on Django1.6, and application B is based on Django1.7. How can this problem be managed.

To solve the above problems, we will introduce virtualenv and virtualenvwrapper.

Virtualenv

From the official virtualenv website https://virtualenv.pypa.io/en/latest/virtualenv.html#:

"The basic problem being addressed is one of dependencies and versions, and indirectly permissions. imagine you have an application that needs version 1 of LibFoo, but another application requires version 2. how can you use both these applications? If you install everything into/usr/lib/python2.7/site-packages (or whatever your platform's standard location is ), it's easy to end up in a situation where you unintentionally upgrade an application that shouldn't be upgraded.

Or more generally, what if you want to install an applicationAnd leave it be? If an application works, any change in its libraries or the versions of those libraries can break the application.

Also, what if you can't install packages into the global site-packages directory? For instance, on a shared host ."

Virtualenv is used to create multiple independent python runtime environments on a machine:

L isolate third-party package dependencies between projects

L install the new Python software package without permission

In addition, there is an additional benefit: when deploying an application, you can package the virtual environment of the development environment into the production environment.

Install

Method 1: Use pip

[Sudo] pip install virtualenv

Method 2: source code

Download and decompress Cd virtualenv-X.X [Sudo] python setup. py install

Method N...

Use Create a virtual environment

Virtualenv [Virtual Environment name]/virtualevn.exe [Virtual Environment name]

My environment is windows python3.4, so as to create a virtual environment:

E: \> D: \ Python34 \ Scripts \ virtualenv.exe env_py3.4

Using base prefix 'd: \ python34'

New python executable in env_py3.4 \ Scripts \ python.exe

Installing setuptools, pip... done.

After the virtual environment env_py3.4 is created, the corresponding directory contains the following folders:

E: \ env_py3.4 directory

<DIR>.

<DIR> ..

2014/05/16 :34 <DIR> Include

<DIR> Lib

<DIR> Scripts

Here, Lib/site-packages contains the libraries installed from the python3.4 system. By default, the virtual environment depends on the site packages in the system environment, that is, the third-party packages installed in the system will also be installed in the virtual environment. If you do not want to rely on these packages, you can add the -- no-site-packages parameter to create a virtual environment.

Virtualenv -- no-site-packages [Virtual Environment name]

Enable Virtual Environment

Source bin/activate or Scripts \ activate. bat

After the virtual environment is enabled, the command line prompt is prefixed with the virtual environment name, as shown in figure(Env_py3.4)E: \ env_py3.4>. You can also print out OS. sys. path in python for verification. For example, after the env_py3.4 virtual environment is enabled, the system path is as follows:

E: \ env_py3.4>Scripts \ activate

(Env_py3.4)E: \ env_py3.4> python

Python 3.4.0 (v3.4.0: 04f714765c13, Mar 16 2014, 19:24:06) [MSC v.1600 32 bit (In

Tel)] on win32

Type "help", "copyright", "credits" or "license" for more information.

>>> Import OS

>>>Print (OS. sys. path)

['', 'E: \ env_py3.4 \ Scripts \ python34.zip ', 'e: \ env_py3.4 \ DLLs', 'e: \ env_py3

. 4 \ lib ', 'e: \ env_py3.4 \ Scripts', 'd: \ Python34 \ Lib ', 'd: \ Python34 \ DLLs ','

E: \ env_py3.4 ', 'e: \ env_py3.4 \ lib \ site-packages']

From OS. sys. path, we can see that all operations related to python in this environment are limited to virtual environments.

Exit the Virtual Environment

Bin/deactivate or Scripts \ deactivate

If you exit the env_py3.4 virtual environment, the prefix of the command line prompt is changed accordingly.

(Env_py3.4) E: \ env_py3.4> Scripts \ deactivate

E: \ env_py3.4>

Install the new python software package in the virtual environment. It is the same as normal python, and pip, easy_install, and other tools are included in the virtual environment for convenient use.

Virtualenvwrapper

Virtualenvwrapper is a Virtualenv extension that makes it easier to manage virtual environments. Virtualenvwrapper provides the following functions:

L integrate all virtual environments into one directory.

L manage (add, remove, and copy) all virtual environments.

L you can use a command to switch the virtual environment.

L Tab to complete the name of the virtual environment.

L each operation provides a user-defined hooks.

L you can write an extension plugin system that is easy to share.

Install

Install virtualenvwrapper Through pip or easy_install

Pip install virtualenvwrapper

By default, virtualenvwrapper is installed under/usr/local/bin. In fact, you need to run the virtualenvwrapper. sh file.

Note: virtualenvwrapper is a set of shell functions defined in Bourne shell compatible syntax. So in the window platform, is not used, but there is a virtualenvwrapper-win version (https://pypi.python.org/pypi/virtualenvwrapper-win ).

Virtualenvwrapper-win will be installed under the python root directory, such as D: \ Python34.

# using pip
 

pip install virtualenvwrapper-win
 

# using easy_install
 

easy_install virtualenvwrapper-win
 

# from source
 

git clone git://github.com/davidmarble/virtualenvwrapper-win.git
 

cd virtualenvwrapper-win
 

python setup.py install
 

Use

Virtualenvwrapper-win and virtualenvwrapper are used in the same way:

L list Virtual Environments: workon or lsvirtualenv

L create a virtual environment: mkvirtualenv [Virtual Environment name]

L start/switch the virtual environment: workon [Virtual Environment name]

L delete a virtual environment: rmvirtualenv [Virtual Environment name]

L leave the virtual environment: deactivate.

For example, I have created three virtual environments.

.......

(Vn_py3.4_app2) D: \ Python34>Mkvirtualenv. bat vn_py3.4_app3

Using base prefix 'd: \ python34'

New python executable in vn_py3.4_app3 \ Scripts \ python.exe

Installing setuptools, pip... done.

(Vn_py3.4_app3) D: \ Python34>Workon. bat

Pass a name to activate one of the following virtualenvs:

========================================================== ============================

Vn_py3.4_app1

Vn_py3.4_app2

Vn_py3.4_app3

The default Virtual Environment path is % USERPROFILE % \ Envs, that is, C: \ Users \ User Name \ Envs.

Switch the virtual environment:

(Vn_py3.4_app3) D: \ Python34>Workon. bat vn_py3.4_app1

(Vn_py3.4_app1)D: \ Python34>Workon. bat vn_py3.4_app2

(Vn_py3.4_app2)D: \ Python34>

Note: If the windowRun the following command D: \ Python34 \ Scripts> mkvirtualenv. bat F: \ evn_py3.4_app1:

Python.exe: can't open file 'd: \ Python34 \ Scripts \ virtualenv-script.py ': [Errno 2

] No such file or directory, Modify mkvirtualenv. batPython.exe "% PYHOME % \ Scripts \ virtualenv-script.py" % ARGS % =Export python.exe "% PYHOME % \ Scripts \ virtualenv.exe" % ARGS %You can.

Summary

Based on virtualenv + virtualenvwrapper, Environment isolation can be well completed to ensure that the environment for each application is clean. In addition, for a clean environment, you can use:

Pip freeze> requirements.txtKeep the package dependency information in the requirements.txt File

Pip install-r requirements.txtAll packages are automatically downloaded and installed from the Internet.

This facilitates application deployment and distribution. next article about pip software package management.

Related connections:

Https://virtualenv.pypa.io/en/latest/index.html

Http://virtualenvwrapper.readthedocs.org/en/latest/index.html

Https://pypi.python.org/pypi/virtualenvwrapper-win