Python虛擬環境配置

VirtualEnv用於在一臺機器上建立多個獨立的python執行環境，VirtualEnvWrapper為前者提供了一些便利的命令列上的封裝。

1.安裝virtualenv

pip install virtualenv   #py2安裝

1.1 virtualenv建立虛擬環境並進入使用

說明文件

You must provide a DEST_DIR
Usage: virtualenv [OPTIONS] DEST_DIR

Options:
  --version             show program's version number and exit
 

  -h, --help            show this help message and exit
  -v, --verbose         Increase verbosity.
  -q, --quiet           Decrease verbosity.
  -p PYTHON_EXE, --python=PYTHON_EXE
                        The Python interpreter to use, e.g.,
                        --python=python2.5 will use the python2.5 interpreter
 

                        to create the new environment.  The default is the
                        interpreter that virtualenv was installed with
                        (/usr/bin/python)
  --clear               Clear out the non-root install and start from scratch.
  --no-site-packages    DEPRECATED. Retained only
 
 for backward compatibility.
                        Not having access to global site-packages is now the
                        default behavior.
  --system-site-packages
                        Give the virtual environment access to the global
                        site-packages.
  --always-copy         Always copy files rather than symlinking.
  --unzip-setuptools    Unzip Setuptools when installing it.
  --relocatable         Make an EXISTING virtualenv environment relocatable.
                        This fixes up scripts and makes all .pth files
                        relative.
  --no-setuptools       Do not install setuptools in the new virtualenv.
  --no-pip              Do not install pip in the new virtualenv.
  --no-wheel            Do not install wheel in the new virtualenv.
  --extra-search-dir=DIR
                        Directory to look for setuptools/pip distributions in.
                        This option can be used multiple times.
  --download            Download preinstalled packages from PyPI.
  --no-download, --never-download
                        Do not download preinstalled packages from PyPI.
  --prompt=PROMPT       Provides an alternative prompt prefix for this
                        environment.
  --setuptools          DEPRECATED. Retained only for backward compatibility.
                        This option has no effect.
  --distribute          DEPRECATED. Retained only for backward compatibility.
                        This option has no effect.

• 安裝需要版本的python

• 指定virtualenv中的python版本

  virtualenv --no-site-packages --python=2.7 env
  

Note:

1. 建立virtualenv虛擬環境之前，系統中必須要安裝有對應版本的python，並且解除安裝之後當前虛擬環境就無效了。系統中可以同時存在python2和python3，通過環境變數中的系統變數path（不是使用者變數）控制cmd或者系統中使用哪個版本的python，哪個版本的路徑在前面就優先使用哪個版本。

2. –no-site-packages表示不包括系統全域性的Python安裝包，這樣會更令環境更乾淨

3. –python=python2.7指定Python的版本未系統已經安裝了的Python2.7

4. env是建立的虛擬環境名稱

5. 沒有安裝python2.7或者使用命令virtualenv –no-site-packages –python=python2.7 env會出現The executable python does notexist 錯誤

1.2進入虛擬環境並激活

$ . env/bin/activate

1.3退出虛擬環境

$ deactivate

1.4刪除虛擬環境

$ rm -r venv

2.virtualenvwrapper

2.1 pip安裝virtualenvwrapper

$ pip install virtualenvwrapper

2.2 初始化

將初始化檔案寫入使用者環境變數

$ vi .bashrc

# 加入下面兩行配置
source /usr/local/bin/virtualenvwrapper.sh
# 虛擬環境指定路徑，不指定預設使用~/.virtualenvs
export WORKON_HOME="虛擬環境絕對路徑"

• 建立：mkvirtualenv [虛擬環境名稱]
• 刪除：rmvirtualenv [虛擬環境名稱]
• 進入：workon [虛擬環境名稱]
• 退出：deactivate

所有的虛擬環境，都位於/home/.virtualenvs目錄下

建立指定版的虛擬環境：

yangqian@ubuntu:~$ mkvirtualenv -p python3.5 test-3.5