Python module package call analysis

  Original http://wuyanzan60688.blog.163.com/blog/static/1277761632011102113211189/

A

   |----- __init__.py

   |-----  a.py

   |---------B

         |--------- __init__.py

         |---------b.py

   |---------C

         |--------- __init__.py

         |--------c.py

As shown in the structure tree, B and C belong to A's subdirectories, but B and C are parallel. . .

The codes of b.py and c.py are as follows:

b.py：

def b_hello():
    print "B_HELLO"
c.py：

def c_hello():
    print "C_HELLO"

If a.py in A wants to call py in B or C, it can be called as follows (take B as an example)

from B import b

b.b_hello()

Operation result: B_HELLO

But what if py in B or C calls B or C?

At this time, if we still use the call as mentioned above, an error will be reported (here is b.py calling c.py)

>>>

Traceback (most recent call last):
  File "E:\testnow\A\B\b.py", line 1, in <module>
    from C import c
ImportError: No module named C

So, this method does not work, how to do it, as follows

import sys
sys.path.append('E:\\testnow\\A\\C')
import c
def b_hello():
    print "B_HELLO"
c.c_hello()
用这种方法，输出结果是：C_HELLO

也即刚才上面的“from 文件夹 import 模块名”只适用于父目录调用子目录的情况。。。而第二种方法则对所有的情况都适用，包括两个模块甚至都不在一个盘的情况。。。这里需要注意的一点是：sys.path添加目录时注意是在windows还是在linux下，windows下需要‘\\’否则会出错。。。。。。。（我在这点上走了很久的弯路。。。）