python虚拟环境

作用

让同一台计算机上不同的项目使用独立的python开发环境
可以使用不同版本的第三方库

windows上安装virtualenv

• 打开命令行 执行 pip install virtulenv
• 如果安装失败可以尝试pip install –upgrade virtualenv

C:\Users\Mark>pip install virtulenv
Collecting virtulenv
  Could not find a version that satisfies the requirement virtulenv (from versions: )
No matching distribution found for virtulenv

----------------发现报错了--------------
C:\Users\Mark>pip install --upgrade virtualenv
Collecting virtualenv
  Downloading virtualenv-15.1.0-py2.py3-none-any.whl (1.8MB)
    100% |████████████████████████████████| 1.8MB 25kB/s
Installing collected packages: virtualenv
Successfully installed virtualenv-15.1.0
----尝试使用pip install --upgrade virtualenv也报错--------
不过重复执行几次之后终于成功了

创建virtualenv

• 首先创建一个用于存放虚拟环境的文件夹
• 使用virtualenv flask-env(虚拟环境名称) 创建虚拟环境

C:\>mkdir pyenv
C:\>cd pyenv
C:\pyenv>virtualenv flask-env
Using base prefix 'c:\\python\\python36'
New python executable in C:\pyenv\flask-env\Scripts\python.exe
Installing setuptools, pip, wheel...done.

C:\pyenv>

激活虚拟环境

• 进入新创建的虚拟环境中的Scripts文件夹下执行activate命令
• Linux 进入虚拟环境的bin目录下执行activate

C:\pyenv\flask-env\Scripts>activate

(flask-env) C:\pyenv\flask-env\Scripts>

退出当前虚拟环境回到全局环境中

• 执行deactivate命令

使用虚拟环境需要另外安装属于虚拟环境自己的软件包

• 进入虚拟环境的scripts下 执行activate
• 执行pip install xx

C:\pyenv\flask-env\Scripts>activate

(flask-env) C:\pyenv\flask-env\Scripts>deactivate
C:\pyenv\flask-env\Scripts>activate

(flask-env) C:\pyenv\flask-env\Scripts>pip install flask
Collecting flask
  Using cached Flask-0.12.2-py2.py3-none-any.whl
Collecting itsdangerous>=0.21 (from flask)
  Using cached itsdangerous-0.24.tar.gz
Collecting click>=2.0 (from flask)
  Using cached click-6.7-py2.py3-none-any.whl
Collecting Werkzeug>=0.7 (from flask)
  Using cached Werkzeug-0.12.2-py2.py3-none-any.whl
Collecting Jinja2>=2.4 (from flask)
  Using cached Jinja2-2.9.6-py2.py3-none-any.whl
Collecting MarkupSafe>=0.23 (from Jinja2>=2.4->flask)
  Using cached MarkupSafe-1.0.tar.gz
Building wheels for collected packages: itsdangerous, MarkupSafe
  Running setup.py bdist_wheel for itsdangerous ... done
  Stored in directory: C:\Users\Mark\AppData\Local\pip\Cache\wheels\fc\a8\66\24d655233c757e178d45dea2de22a04c6d92766abfb741129a
  Running setup.py bdist_wheel for MarkupSafe ... done
  Stored in directory: C:\Users\Mark\AppData\Local\pip\Cache\wheels\88\a7\30\e39a54a87bcbe25308fa3ca64e8ddc75d9b3e5afa21ee32d57
Successfully built itsdangerous MarkupSafe
Installing collected packages: itsdangerous, click, Werkzeug, MarkupSafe, Jinja2, flask
Successfully installed Jinja2-2.9.6 MarkupSafe-1.0 Werkzeug-0.12.2 click-6.7 flask-0.12.2 itsdangerous-0.24

(flask-env) C:\pyenv\flask-env\Scripts>python
Python 3.6.0 (v3.6.0:41df79263a11, Dec 23 2016, 08:06:12) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import flask
>>> print flask.__version__
  File "<stdin>", line 1
    print flask.__version__
              ^
SyntaxError: Missing parentheses in call to 'print'
>>> print(flask.__version__)
0.12.2
>>>