python如何通過(guò)_X和all隱藏模塊數(shù)據(jù)

1.1 描述

python的_X指出不被復(fù)制的變量，all指出要復(fù)制的變量。

1.2 模塊_X

文件內(nèi)容

pkgmoda.py

import os
print('run:{}'.format(os.path.abspath(__file__)))
s='梯閱線條'
_a='tyxt'
b=9555

from module import * 不復(fù)制_X變量

# cmd 執(zhí)行下面命令
C:UsersAdministrator>e:&cd E:documentsF盤(pán)
E:documentsF盤(pán)>d:python3python
Python 3.7.8 (tags/v3.7.8:4b47a5b6ba, Jun 28 2020, 07:55:33) [MSC v.1916 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
# from module import * 不復(fù)制_X變量
>>> from pkg.moda import *
run:E:documentsF盤(pán)pkg__init__.py
run:E:documentsF盤(pán)pkgmoda.py
# 復(fù)制非單下劃線開(kāi)頭變量，可訪問(wèn)
>>> s
'梯閱線條'
>>> b
9555
# 不復(fù)制單下劃線開(kāi)頭變量，不可訪問(wèn)
>>> _a
Traceback (most recent call last):
 File "", line 1, in 
NameError: name '_a' is not defined

單下劃線開(kāi)頭變量，對(duì)非from的import語(yǔ)句無(wú)效，會(huì)被復(fù)制。

# cmd 執(zhí)行下面命令
E:documentsF盤(pán)>d:python3python
Python 3.7.8 (tags/v3.7.8:4b47a5b6ba, Jun 28 2020, 07:55:33) [MSC v.1916 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
# _X對(duì)import 語(yǔ)句無(wú)效
>>> import pkg.moda
run:E:documentsF盤(pán)pkg__init__.py
run:E:documentsF盤(pán)pkgmoda.py
>>> pkg.moda.s
'梯閱線條'
>>> pkg.moda.b
9555
# 可訪問(wèn)_a
>>> pkg.moda._a
'tyxt'

1.3 模塊all

文件內(nèi)容

pkgmodb.py

import os
__all__=['s','b',]
print('run:{}'.format(os.path.abspath(__file__)))
s='梯閱線條'
a='tyxt'
b=9555

from module import *，只復(fù)制all列表內(nèi)變量，用于模塊文件

# cmd 執(zhí)行下面命令
E:documentsF盤(pán)>d:python3python
Python 3.7.8 (tags/v3.7.8:4b47a5b6ba, Jun 28 2020, 07:55:33) [MSC v.1916 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from pkg.modb import *
run:E:documentsF盤(pán)pkg__init__.py
run:E:documentsF盤(pán)pkgmodb.py
# 在__all__列表的變量，可訪問(wèn)
>>> s
'梯閱線條'
>>> a
# 不在__all__列表的變量，不可訪問(wèn)
Traceback (most recent call last):
 File "", line 1, in 
NameError: name 'a' is not defined
>>> b
9555

all列表，對(duì)非from的import語(yǔ)句無(wú)效，不在列表內(nèi)的變量也會(huì)被復(fù)制，可訪問(wèn)。

# cmd 執(zhí)行下面命令
E:documentsF盤(pán)>d:python3python
Python 3.7.8 (tags/v3.7.8:4b47a5b6ba, Jun 28 2020, 07:55:33) [MSC v.1916 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg.modb
run:E:documentsF盤(pán)pkg__init__.py
run:E:documentsF盤(pán)pkgmodb.py
>>> pkg.modb.s
'梯閱線條'
# 不在__all__列表的變量，也可訪問(wèn)
>>> pkg.modb.a
'tyxt'
>>> pkg.modb.b
9555

1.4 包all

文件內(nèi)容

pkg__init__.py

import os
__all__=['moda',]
print('run:{}'.format(os.path.abspath(__file__)))

from pkg import *，自動(dòng)導(dǎo)入all列表內(nèi)模塊，用于包文件 init .py；

# cmd 執(zhí)行下面命令
E:documentsF盤(pán)>d:python3python
Python 3.7.8 (tags/v3.7.8:4b47a5b6ba, Jun 28 2020, 07:55:33) [MSC v.1916 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from pkg import *
run:E:documentsF盤(pán)pkg__init__.py
run:E:documentsF盤(pán)pkgmoda.py
# 自動(dòng)導(dǎo)入 __all__ 列表內(nèi)模塊
>>> moda.s
'梯閱線條'
# 非 __all__ 列表內(nèi)模塊不自動(dòng)導(dǎo)入，不可訪問(wèn)
>>> modb.s
Traceback (most recent call last):
 File "", line 1, in 
NameError: name 'modb' is not defined
>>> modc.s
Traceback (most recent call last):
 File "", line 1, in 
NameError: name 'modc' is not defined