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搭建Python獨立環(huán)境:virtualenv的應(yīng)用

更新時間:2018-07-27 來源:黑馬程序員技術(shù)社區(qū) 瀏覽量:

virtualenv簡介和安裝

virtualenv是Github上的一個項目,按照它的原話就是『Python虛擬環(huán)境的構(gòu)建者』,這是它的項目地址:Virtual Python Environment builder

這里簡單介紹下它的工作原理:virtualenv把運(yùn)行Python程序必須的基本環(huán)境,包括二進(jìn)制Python自身、Python標(biāo)準(zhǔn)庫、pip安裝器,以及至關(guān)重要的site-packages目錄,全部拷貝一份到一個完全隔離的目錄下,這個目錄就是你的獨立開環(huán)境

在項目首頁最下面有安裝教程的超鏈接:Installation,你可以簡單敲pip命令進(jìn)行安裝,這是最簡便的方法

pip install virtualenv

另外還用第二種方法:把項目整個當(dāng)下來,然后手動安裝

# Use virtualenv globally
$ curl -O https://pypi.python.org/packages ... rtualenv-X.X.tar.gz
$ tar xvfz virtualenv-X.X.tar.gz
$ cd virtualenv-X.X
$ [sudo] python setup.py install

# Use virtualenv locally
$ curl -O https://pypi.python.org/packages ... rtualenv-X.X.tar.gz
$ tar xvfz virtualenv-X.X.tar.gz
$ cd virtualenv-X.X
$ python virtualenv.py myVE
事實上你需要全局安裝的Python套件只有兩個,即pip和virtualenv,如果 把virtualenv包括的pip算進(jìn)去,那其實只要安裝一個virtualenv已足矣

使用virtualenv創(chuàng)建獨立項目

在安裝好virtualenv后,就可以創(chuàng)建隔離環(huán)境的Python項目了,下面以demo這個項目為例

1. 創(chuàng)建項目根目錄,命名為demo并進(jìn)入該目錄

?  ~ mkdir demo
?  ~ cd demo
?  demo 

2. 使用virtualenv命令,建議加上–no-site-packages選項

?  demo virtualenv --no-site-packages venv
Using base prefix '/Library/Frameworks/Python.framework/Versions/3.6'
New python executable in /Users/macbookpro/demo/venv/bin/python3.6
Also creating executable in /Users/macbookpro/demo/venv/bin/python
Installing setuptools, pip, wheel...done.

3. 如果想要手動指定Python版本,請使用–python=$PYTHON_VERSION選項

?  demo virtualenv --python=python2.7 --no-site-packages venv1
Running virtualenv with interpreter /usr/local/bin/python2.7
New python executable in /Users/macbookpro/demo/venv1/bin/python2.7
Also creating executable in /Users/macbookpro/demo/venv1/bin/python
Installing setuptools, pip, wheel...done.

4. 你甚至可以指定系統(tǒng)沒有安裝的Python版本,比如我這里的Python3.7,但是絕對不要想當(dāng)然的填寫Pyhton版本號否則會報錯“doesn’t exist”

?  demo virtualenv --python=python3.7 --no-site-packages venv2
Running virtualenv with interpreter /usr/local/bin/python3.7
Using base prefix '/usr/local/Cellar/python/3.7.0/Frameworks/Python.framework/Versions/3.7'
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/virtualenv.py:1041: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
  import imp
New python executable in /Users/macbookpro/demo/venv2/bin/python3.7
Also creating executable in /Users/macbookpro/demo/venv2/bin/python
Installing setuptools, pip, wheel...done.
?  demo virtualenv --python=python4.0 --no-site-packages venv3
The path python4.0 (from --python=python4.0) does not exist


5. 在新建的venv目錄下,重點關(guān)注bin目錄,它包括了pip管理器和python對應(yīng)版本的解釋器Pythonx.x.

?  venv ls
bin                include            lib                pip-selfcheck.json
?  venv cd bin
?  bin ls
activate         easy_install     pip3.6           python3.6
activate.csh     easy_install-3.6 python           wheel
activate.fish    pip              python-config
activate_this.py pip3             python3

?  demo venv/bin/pip install requests
Collecting requests
  Downloading https://files.pythonhosted.org/p ... y2.py3-none-any.whl (91kB)
    100% |████████████████████████████████| 92kB 138kB/s 
Collecting idna<2.8,>=2.5 (from requests)
  Downloading https://files.pythonhosted.org/p ... y2.py3-none-any.whl (58kB)
    100% |████████████████████████████████| 61kB 52kB/s 
Collecting urllib3<1.24,>=1.21.1 (from requests)
  Downloading https://files.pythonhosted.org/p ... y2.py3-none-any.whl (133kB)
    100% |████████████████████████████████| 143kB 29kB/s 
Collecting chardet<3.1.0,>=3.0.2 (from requests)
  Downloading https://files.pythonhosted.org/p ... y2.py3-none-any.whl (133kB)
    100% |████████████████████████████████| 143kB 53kB/s 
Collecting certifi>=2017.4.17 (from requests)
  Downloading https://files.pythonhosted.org/p ... y2.py3-none-any.whl (150kB)
    100% |████████████████████████████████| 153kB 41kB/s 
Installing collected packages: idna, urllib3, chardet, certifi, requests
Successfully installed certifi-2018.4.16 chardet-3.0.4 idna-2.7 requests-2.19.1 urllib3-1.23


6. 用virtual內(nèi)置pip安裝的包被放在lib目錄下

?  demo venv/bin/pip show requests
Name: requests
Version: 2.19.1
Summary: Python HTTP for Humans.
Home-page: http://python-requests.org
Author: Kenneth Reitz
Author-email: me@kennethreitz.org
License: Apache 2.0
Location: /Users/macbookpro/demo/venv/lib/python3.6/site-packages
Requires: idna, certifi, chardet, urllib3
Required-by:

7. 為了減少打字,可激活activate文件,這樣原來的venv/bin/pip就要寫pip,代替了系統(tǒng)原來的pip命令,不用時激活deactivate命令即可

?  demo source venv/bin/activate
(venv) ?  demo pip list
Package    Version  
---------- ---------
certifi    2018.4.16
chardet    3.0.4    
idna       2.7      
pip        10.0.1   
requests   2.19.1   
setuptools 40.0.0   
urllib3    1.23     
wheel      0.31.1   
(venv) ?  demo pip uninstall requests
Uninstalling requests-2.19.1:
  Would remove:
    /Users/macbookpro/demo/venv/lib/python3.6/site-packages/requests-2.19.1.dist-info/*
    /Users/macbookpro/demo/venv/lib/python3.6/site-packages/requests/*
Proceed (y/n)? y
  Successfully uninstalled requests-2.19.1
(venv) ?  demo pip list
Package    Version  
---------- ---------
certifi    2018.4.16
chardet    3.0.4    
idna       2.7      
pip        10.0.1   
setuptools 40.0.0   
urllib3    1.23     
wheel      0.31.1   
(venv) ?  demo 
(venv) ?  demo deactivate 
?  demo 


8. pip和virtualenv合作使用起來很爽,pip使用-r參數(shù)指定requirement文件

pip install -r requirements.txt
1
ok,這樣基本的隔離Python開發(fā)環(huán)境就被創(chuàng)建出來啦~關(guān)于virtualenv暫就講到這里,還有些比較方便的功能有待大家共同探索^ ^

參考 
?_? A non-magical introduction to Pip and Virtualenv for Python beginners 
?_? Requirements Files

備注:Python2.x和3.x的site-packages目錄 
Python2.7:/Library/Python/2.7/site-packages 
Python3.6:/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages


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