最後更新: 2019-08-20

介紹

virtualenv - a tool to create isolated Python environments.

 

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Usage

 

# Install

# epel

yum install python-virtualenv

# The basic usage

# 建立名叫 ENV 的 virtualenv

virtualenv ENV                     # Size >= 12M

它會建立一個 Folder 叫 "ENV", 內有

 - ENV/lib/pythonX.X/site-packages

 - ENV/bin/python

# activate that virtual environment

source ENV/bin/activate

# 行完 script 後, shell prompt 會變成

(VIRTUAL_ENV_DISABLE_PROMPT)  <-- 在這個例子, 它是 ENV

# 安裝要的 package (pip)

i.e.

pip install --upgrade pip

pip install sqlalchemy

pip install MySQL-python

# 離開 virtual environment

deactivate       # to undo the changes to your $PATH.

i.e.

(venv-vncdotool) server:script# deactivate

# Script 內應用

以後只要某 script 想用另一個 ENV, 那只要加以下一句在檔頭即可

#!/path/to/ENV/bin/python

.........................

 

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Setup a Python Virtual Environment [進階]

 

# Create a new virtual environment

virtualenv --no-site-packages --distribute px

OR

# use a Python interpreter(/usr/bin/python26) of your choice

virtualenv -p /usr/bin/python26 venv

* --distribute option to use the setuptools fork Distribute.

* --no-site-packages flag is deprecated; it is now the default behavior. (debian7)

   (not include the packages that are installed globally)

 

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應用

 

應用1: keep your environment consistent

# “freeze” the current state of the environment packages

pip freeze > requirements.txt

# list of all the packages in the current environment

cat requirements.txt

#  re-create the environment

virtualenv ENV

source venv-vncdo/bin/activate

pip install -r requirements.txt

 

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Troubleshoot

 

[問題1] 行 "virtualenv -p python3 py3" 時遇到 error

解決

pip install --upgrade virtualenv

 

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move python virtualenv to another folder (or renaming)

 

By default virtualenv does not support the renaming of environments.

It is safer to just delete the virtualenv directory and create a new one

# 可能方案

[A]

pip install virtualenvwrapper

cpvirtualenv <wrong_name> <correct_name>

rmvirtualenv <wrong_name>

[B]

1. change the $VIRTUAL_ENV environment variable in the myvenv/bin/activate script

2. --relocatable     # Make an EXISTING virtualenv environment relocatable. (relative path)

virtualenv --relocatable venv-vncdo

如果有以下 Error, 那就要重安了

Script /mydata/script/reset_win7/venv-vncdo/bin/vncdo cannot be made relative
 (it's not a normal script that starts with #!/mydata/script/reset_win7/venv-vncdo/bin/python)

Absolute path is still hardcoded in the activate script @@||

 

 

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Doc

 

http://www.virtualenv.org/en/latest/virtualenv.html#usage

 

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