python 路径

 https://leemendelowitz.github.io/blog/how-does-python-find-packages.html

https://www.cnblogs.com/qingspace/p/5284480.html

 

-  按照Python的约定，需要在animal文件夹中创建名为__init__.py的空文本文件，以标识animal文件夹是一个包。

-  用from关键字直接导入模块内的属性或方法

-  搜索 sys.path

 -默认情况下Python还是需要导入包内的具体模块的，但有个变通的办法，就是使用包中__init__.py文件，提前准备包内需要被引用的各个模块中的变量，类似于向外部引用者暴露包内接口。__init__.py文件代码是在包或者包  内模块被引用时执行的，因而可以在其中做一些初始化的工作。修改animal文件夹中__init__.py文件如下，其中模块可以使用绝对路径和相对路径，相对路径中一个句点.代表同级目录，两个句点..代表父目录。

 

https://blog.csdn.net/qq_15505637/article/details/80908751 

-  python – dist-packages和site-packages有什么区别？
             sudo apt-get install 安装的package存放在 /usr/lib/python2.7/dist-packages目录中
             pip 或者 easy_install安装的package存放在/usr/local/lib/python2.7/dist-packages目录中
             手动从源代码安装的package存放在site-packages目录

me@me:~/me$ python
Python 2.7.15+ (default, Nov 27 2018, 23:36:35)
[GCC 7.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.path
['', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-aarch64-linux-gnu', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/home/me/.local/lib/python2.7/site-packages', '/usr/local/lib/python2.7/dist-packages', '/usr/local/lib/python2.7/dist-packages/torchvision-0.3.0a0+4c56f42-py2.7-linux-aarch64.egg', '/usr/local/lib/python2.7/dist-packages/Pillow-6.0.0-py2.7-linux-aarch64.egg', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/gtk-2.0']
>>>

　　

以下实验证明python搜了torchvision的egg文件。

>>> import sys
>>> sys.path
['', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-aarch64-linux-gnu', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/home/me/.local/lib/python2.7/site-packages', '/usr/local/lib/python2.7/dist-packages', '/usr/local/lib/python2.7/dist-packages/torchvision-0.3.0a0+4c56f42-py2.7-linux-aarch64.egg', '/usr/local/lib/python2.7/dist-packages/Pillow-6.0.0-py2.7-linux-aarch64.egg', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/gtk-2.0']
>>> print '\n'.join(sys.path)

/usr/lib/python2.7
/usr/lib/python2.7/plat-aarch64-linux-gnu
/usr/lib/python2.7/lib-tk
/usr/lib/python2.7/lib-old
/usr/lib/python2.7/lib-dynload
/home/me/.local/lib/python2.7/site-packages
/usr/local/lib/python2.7/dist-packages
/usr/local/lib/python2.7/dist-packages/torchvision-0.3.0a0+4c56f42-py2.7-linux-aarch64.egg
/usr/local/lib/python2.7/dist-packages/Pillow-6.0.0-py2.7-linux-aarch64.egg
/usr/lib/python2.7/dist-packages
/usr/lib/python2.7/dist-packages/gtk-2.0
>>> print( '\n'.join(sys.path) )

/usr/lib/python2.7
/usr/lib/python2.7/plat-aarch64-linux-gnu
/usr/lib/python2.7/lib-tk
/usr/lib/python2.7/lib-old
/usr/lib/python2.7/lib-dynload
/home/me/.local/lib/python2.7/site-packages
/usr/local/lib/python2.7/dist-packages
/usr/local/lib/python2.7/dist-packages/torchvision-0.3.0a0+4c56f42-py2.7-linux-aarch64.egg
/usr/local/lib/python2.7/dist-packages/Pillow-6.0.0-py2.7-linux-aarch64.egg
/usr/lib/python2.7/dist-packages
/usr/lib/python2.7/dist-packages/gtk-2.0
>>> print( '\n'.join(sys.path) )

/usr/lib/python2.7
/usr/lib/python2.7/plat-aarch64-linux-gnu
/usr/lib/python2.7/lib-tk
/usr/lib/python2.7/lib-old
/usr/lib/python2.7/lib-dynload
/home/me/.local/lib/python2.7/site-packages
/usr/local/lib/python2.7/dist-packages
/usr/local/lib/python2.7/dist-packages/torchvision-0.3.0a0+4c56f42-py2.7-linux-aarch64.egg
/usr/local/lib/python2.7/dist-packages/Pillow-6.0.0-py2.7-linux-aarch64.egg
/usr/lib/python2.7/dist-packages
/usr/lib/python2.7/dist-packages/gtk-2.0
>>> import torchvision
>>>

me@me:~/me$ sudo mv /usr/local/lib/python2.7/dist-packages/torchvision-0.3.0a0+4c56f42-py2.7-linux-aarch64.egg /tmp/

me@me:/tmp$ python
Python 2.7.15+ (default, Nov 27 2018, 23:36:35)
[GCC 7.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> print( '\n'.join(sys.path) )

/usr/lib/python2.7
/usr/lib/python2.7/plat-aarch64-linux-gnu
/usr/lib/python2.7/lib-tk
/usr/lib/python2.7/lib-old
/usr/lib/python2.7/lib-dynload
/home/me/.local/lib/python2.7/site-packages
/usr/local/lib/python2.7/dist-packages
/usr/local/lib/python2.7/dist-packages/Pillow-6.0.0-py2.7-linux-aarch64.egg
/usr/lib/python2.7/dist-packages
/usr/lib/python2.7/dist-packages/gtk-2.0
>>>
>>> import torchvision
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named torchvision
>>>