Python官方文档参考链接: 常规包

Python 定义了两种类型的包，常规包 和 命名空间包。 常规包是传统的包类型，它们在 Python 3.2 及之前就已存在。 常规包通常以一个包含 __init__.py 文件的目录形式实现。 当一个常规包被导入时，这个 __init__.py 文件会隐式地被执行，它所定义的对象会被绑定到该包命名空间中的名称。__init__.py 文件可以包含与任何其他模块中所包含的 Python 代码相似的代码，Python 将在模块被导入时为其添加额外的属性。 例如，以下文件系统布局定义了一个最高层级的 parent 包和三个子包. 导入 parent.one 将隐式地执行 parent/__init__.py 和 parent/one/__init__.py。 后续导入 parent.two 或 parent.three 则将分别执行 parent/two/__init__.py 和 parent/three/__init__.py。

parent\__init__.py:

print("导入parent包...内部已经导入random库")

str_parent = r"我是parent\__init__.py里的字符串..."

import random

parent\two\__init__.py:

print("导入parent/two包...内部已经导入time库")

str_parent_two = r"我是parent\two\__init__.py里的字符串..."

import time

parent\three\__init__.py:

print("导入parent/three包...内部已经导入jieba库")

str_parent_three = r"我是parent\three\__init__.py里的字符串..."

import jieba

parent\one\__init__.py:

print("导入parent/one包...内部已经导入hashlib库")

str_parent_one = r"我是parent\one\__init__.py里的字符串..."

import hashlib

cmd控制台下的操作:

Windows PowerShell

版权所有 (C) Microsoft Corporation。保留所有权利。

尝试新的跨平台 PowerShell https://aka.ms/pscore6

PS C:\Users\chenxuqi\Desktop\新建文件夹\测试包> python

Type "help", "copyright", "credits" or "license" for more information.

>>> import parent

导入parent包...内部已经导入random库

>>> parent.str_parent

'我是parent\\__init__.py里的字符串...'

>>> random

Traceback (most recent call last):

File "", line 1, in

NameError: name 'random' is not defined

>>> parent.random

>>> parent.random.randint(2,7)

7

>>> parent.random.randint(2,7)

7

>>> parent.random.randint(2,7)

7

>>> parent.random.randint(2,7)

7

>>> parent.random.randint(2,7)

7

>>> parent.random.randint(2,9)

5

>>> parent.random.randint(2,9)

2

>>> parent.random.randint(2,9)

3

>>> parent.random.randint(2,9)

8

>>> parent.random.randint(2,7)

5

>>> parent.random.randint(2,7)

2

>>> parent.random.randint(2,7)

5

>>> parent.random.randint(2,7)

6

>>> import parent.two

导入parent/two包...内部已经导入time库

>>> parent.two.str_parent_two

'我是parent\\two\\__init__.py里的字符串...'

>>> parent.two.time

>>> parent.two.time.time()

1605883430.647523

>>> time

Traceback (most recent call last):

File "", line 1, in

NameError: name 'time' is not defined

>>> from parent.two import time

>>> time

>>> now = time.time()

>>> print(time.ctime(now))

Fri Nov 20 22:46:45 2020

>>> import parent.three

导入parent/three包...内部已经导入jieba库

>>> import parent.three as three

>>> three.str_parent_three

'我是parent\\three\\__init__.py里的字符串...'

>>> three.jieba

>>> jieba.lcut("全国计算机等级考试Python科目")

Traceback (most recent call last):

File "", line 1, in

NameError: name 'jieba' is not defined

>>> three.jieba.lcut("全国计算机等级考试Python科目")

Building prefix dict from the default dictionary ...

Dumping model to file cache C:\Users\chenxuqi\AppData\Local\Temp\jieba.cache

Loading model cost 0.857 seconds.

Prefix dict has been built successfully.

['全国', '计算机', '等级', '考试', 'Python', '科目']

>>> from parent.one import str_parent_one

导入parent/one包...内部已经导入hashlib库

>>> str_parent_one

'我是parent\\one\\__init__.py里的字符串...'

>>> from parent.one import hashlib as hsb

>>> hsb

>>> hsb.md5("尹增宝爱听古风音乐".encode("utf8")).hexdigest()

'075649873523f1e621d4b33f69b60ebb'

>>>

>>> hsb.md5("林祖泉".encode("utf8")).hexdigest()

'738974139c96e7c1b174e1f886ffb641'

>>>

>>>

导入一个包之后,无法访问其子包,除非其子包有__init__.py文件,而且该文件已经被执行过一次,那么该包就会有其该子包的属性,否则会报错,比如:AttributeError: module 'parent' has no attribute 'three'

修改./__init__.py文件:

print("导入parent包...内部已经导入random库")

str_parent = r"我是parent\__init__.py里的字符串..."

import random

import parent.one as yi

from parent import two

# import parent.three

cmd控制台下的操作如下:

Windows PowerShell

版权所有 (C) Microsoft Corporation。保留所有权利。

尝试新的跨平台 PowerShell https://aka.ms/pscore6

PS C:\Users\chenxuqi\Desktop\新建文件夹\测试包> python

Python 3.7.4 (tags/v3.7.4:e09359112e, Jul 8 2019, 20:34:20) [MSC v.1916 64 bit (AMD64)] on win32

Type "help", "copyright", "credits" or "license" for more information.

>>> parent

Traceback (most recent call last):

File "", line 1, in

NameError: name 'parent' is not defined

>>> import parent

导入parent包...内部已经导入random库

导入parent/one包...内部已经导入hashlib库

导入parent/two包...内部已经导入time库

>>> parent

>>> parent.one

>>> parent.yi

>>> parent.two

>>> yi

Traceback (most recent call last):

File "", line 1, in

NameError: name 'yi' is not defined

>>> two

Traceback (most recent call last):

File "", line 1, in

NameError: name 'two' is not defined

>>> one

Traceback (most recent call last):

File "", line 1, in

NameError: name 'one' is not defined

>>> three

Traceback (most recent call last):

File "", line 1, in

NameError: name 'three' is not defined

>>> parent.three

Traceback (most recent call last):

File "", line 1, in

AttributeError: module 'parent' has no attribute 'three'

>>> import parent.three

导入parent/three包...内部已经导入jieba库

>>> parent.three

>>> three

Traceback (most recent call last):

File "", line 1, in

NameError: name 'three' is not defined

>>> import parent.three as three

>>> three

>>>

>>>

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