day 4 __all__ 包 __init__.py

1.__all__的作用

• 如果一个文件中有__all__变量，那么也就意味着这个变量中的元素，不会被from xxx import *时导入

__all__ = ["test1","num"]    #只能让调用test1，num1
def test1():
    print("----test1")

def test2():
    print("----test2")

num = 1

class Dog(object):
    pass

In [6]: from sendmsg import *   #只能调用__all__里面规定的方法

In [7]: test1()
----test1

In [8]: test2()
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-8-35ebc1c532fc> in <module>()
----> 1 test2()

NameError: name 'test2' is not defined

In [9]: num
Out[9]: 1

In [10]: Dog()
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-10-ff6dc2469c3e> in <module>()
----> 1 Dog()

NameError: name 'Dog' is not defined
 

In [1]: import sendmsg    #通过这个方式不受影响

In [2]: sendmsg.
sendmsg.Dog    sendmsg.py     sendmsg.test2  
sendmsg.num    sendmsg.test1  

In [2]: sendmsg.
sendmsg.Dog    sendmsg.py     sendmsg.test2  
sendmsg.num    sendmsg.test1  

In [2]: sendmsg.test1()
----test1

In [3]: sendmsg.test2()
----test2

 2.包

•    包：在一个文件夹下有多个模块，并且有个__init__.py文件
• 模块：1个py文件

###   sendmsg.py 
def test1():
    print("--sendmsg-test1---")

####   recvmsg.py 
def test2():
    print("---recvmsg--test2---")
 

　　1）版本1：

.
├── infordisplay.py
└── Msg                     #具有很多模块的集合场所
    ├── recvmsg.py
    └── sendmsg.py

####   IPython 2.4.1     python2认为这只是文件夹

In [1]: import Msg
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-1-32b2df17b362> in <module>()
----> 1 import Msg

ImportError: No module named Msg

###   iPython 3.5.2   python认为此文件夹是包

In [1]: import Msg

In [2]: Msg.sendmsg.test1()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-2-889fe4d38288> in <module>()
----> 1 Msg.sendmsg.test1()

AttributeError: module 'Msg' has no attribute 'sendmsg'

　　2）版本2：__init__.py  让文件夹变成包

.
├── infordisplay.py
└── Msg                    #包
    ├── __init__.py
    ├── recvmsg.py
    └── sendmsg.py

 　　　　

###   IPython 2.4.1

In [1]: import Msg

In [2]: Msg.sendmsg.test1()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-2-889fe4d38288> in <module>()
----> 1 Msg.sendmsg.test1()

AttributeError: 'module' object has no attribute 'sendmsg'

####   Python 3.5.2

In [1]: import Msg

In [2]: Msg.sendmsg.test1()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-2-889fe4d38288> in <module>()
----> 1 Msg.sendmsg.test1()

AttributeError: module 'Msg' has no attribute 'sendmsg'

 　　3）版本3：

###     Msg/__init__.py
__all__ = ["sendmsg"]

print("when import this bag ,do this __init__.py ")

import sendmsg

####    IPython 2.4.1   可以直接执行
###   python3 不能执行


In [1]: import Msg
when import this bag ,do this __init__.py 

In [2]: Msg.sendmsg.test1()
--sendmsg-test1---

 　　4）版本4：最终版本

##      Msg/__init__.py

__all__ = ["sendmsg"]

print("when import this bag ,do this __init__.py ")

from . import sendmsg
    
    #. 当前目录

####   python 2 3 都可以执行
In [1]: import Msg
when import this bag ,do this __init__.py 

In [2]: Ms
Msg   Msg/  

In [2]: Msg.sendmsg.test1()
--sendmsg-test1---