python包模块相对导入from和import介绍2

3.5.3 示例import-python2.7搜索当前包

python2.7先搜索当前包目录，再搜索sys.path模块搜索路径。即先相对再绝对。

本示例在交互模式执行，非文件模式执行。

E**:**\\documents\\F盘\\ 目录不存在pkgmoda.py文件

# 打开cmd，执行下面命令
E:\\documents\\F盘>d:\\Python27\\python
Python 2.7.18 (v2.7.18:8d21aa21f2, Apr 20 2020, 13:25:05) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg1.main_moda
run:E:\\documents\\F盘\\pkg1\\__init__.pyc
print(sys.path[0]):
run:E:\\documents\\F盘\\pkg1\\pkgmoda.pyc
print(string):<module 'string' from 'd:\\Python27\\lib\\string.pyc'>
run:E:\\documents\\F盘\\pkg1\\main_moda.pyc
# 先搜索当前包目录
print(pkgmoda):<module 'pkg1.pkgmoda' from 'pkg1\\pkgmoda.pyc'>
pkgmoda.index:E:\\documents\\F盘\\pkg1\\pkgmoda.pyc

3.5.4 示例import-python3.7略过当前包

python3.7不搜索当前包目录，直接搜索sys.path模块搜索路径，即绝对导入。

本示例在交互模式执行，非文件模式执行。

E**:**\\documents\\F盘\\ 目录不存在pkgmoda.py文件

# 打开cmd，执行下面命令
E:\\documents\\F盘>d:\\python3\\python
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 pkg1.main_moda
run:E:\\documents\\F盘\\pkg1\\__init__.py
print(sys.path[0]):
# 不搜索当前包目录
Traceback (most recent call last):
 File "", line 1, in 
 File "E:\\documents\\F盘\\pkg1\\main_moda.py", line 4, in 
   import pkgmoda
ModuleNotFoundError: No module named 'pkgmoda'

3.5.5 示例import-python3.7程序目录-文件模式

python3.7直接搜索sys.path模块搜索路径，即绝对导入。

本示例在文件模式执行，非交互模式执行。

E**:**\\documents\\F盘\\ 目录不存在pkgmoda.py文件

# 打开cmd，执行下面命令
E:\\documents\\F盘>d:\\python3\\python pkg1\\main_moda.py
# 程序目录为 pkg1
print(sys.path[0]):E:\\documents\\F盘\\pkg1
run:E:\\documents\\F盘\\pkg1\\pkgmoda.py
print(string):<module 'string' from 'd:\\\\python3\\\\lib\\\\string.py'>
run:E:\\documents\\F盘\\pkg1\\main_moda.py
# 搜索sys.path的程序目录
print(pkgmoda):<module 'pkgmoda' from 'E:\\\\documents\\\\F盘\\\\pkg1\\\\pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盘\\pkg1\\pkgmoda.py

3.5.6 示例import-sys.path

将pkg1\\pkgmoda.py剪切到“E**:**\\documents\\F盘”。

当前包目录没有模块，sys.path的程序目录有模块。

python2.7先当前包目录，在sys.path，

python3.7只sys.path。

本示例在交互模式执行，非文件模式执行。

# python2.7示例
E:\\documents\\F盘>d:\\Python27\\python
Python 2.7.18 (v2.7.18:8d21aa21f2, Apr 20 2020, 13:25:05) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg1.main_moda
run:E:\\documents\\F盘\\pkg1\\__init__.pyc
print(sys.path[0]):
run:E:\\documents\\F盘\\pkgmoda.py
print(string):<module 'string' from 'd:\\Python27\\lib\\string.pyc'>
run:E:\\documents\\F盘\\pkg1\\main_moda.py
# 搜索程序目录
print(pkgmoda):<module 'pkgmoda' from 'pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盘\\pkgmoda.py
# python3.7示例
E:\\documents\\F盘>d:\\python3\\python
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 pkg1.main_moda
run:E:\\documents\\F盘\\pkg1\\__init__.py
print(sys.path[0]):
run:E:\\documents\\F盘\\pkgmoda.py
print(string):<module 'string' from 'd:\\\\python3\\\\lib\\\\string.py'>
run:E:\\documents\\F盘\\pkg1\\main_moda.py
# 搜索程序目录
print(pkgmoda):<module 'pkgmoda' from 'E:\\\\documents\\\\F盘\\\\pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盘\\pkgmoda.py

3.5.7 示例from点相对导入

“目录文件内容-1”修改 main_moda.py 为相对导入 from **.**import pkgmoda

# main_moda.py
# coding=utf-8
import sys,os
print('print(sys.path[0]):{}'.format(sys.path[0]))
from . import pkgmoda
print('run:{}'.format(os.path.abspath(__file__)))
print('print(pkgmoda):{}'.format(pkgmoda))
print('pkgmoda.index:{}'.format(pkgmoda.index))

本示例在交互模式执行，非文件模式执行。

E**:**\\documents\\F盘\\ 目录不存在pkgmoda.py文件

相对导入from . import module 从当前包搜索。

# python2.7示例
E:\\documents\\F盘>d:\\Python27\\python
Python 2.7.18 (v2.7.18:8d21aa21f2, Apr 20 2020, 13:25:05) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg1.main_moda
run:E:\\documents\\F盘\\pkg1\\__init__.py
print(sys.path[0]):
run:E:\\documents\\F盘\\pkg1\\pkgmoda.py
print(string):<module 'string' from 'd:\\Python27\\lib\\string.pyc'>
run:E:\\documents\\F盘\\pkg1\\main_moda.py
# python2.7 相对导入从当前包搜索
print(pkgmoda):<module 'pkg1.pkgmoda' from 'pkg1\\pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盘\\pkg1\\pkgmoda.py

# python3.7示例
E:\\documents\\F盘>d:\\python3\\python
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 pkg1.main_moda
run:E:\\documents\\F盘\\pkg1\\__init__.py
print(sys.path[0]):
run:E:\\documents\\F盘\\pkg1\\pkgmoda.py
print(string):<module 'string' from 'd:\\\\python3\\\\lib\\\\string.py'>
run:E:\\documents\\F盘\\pkg1\\main_moda.py
# python3.7 相对导入从当前包搜索
print(pkgmoda):<module 'pkg1.pkgmoda' from 'E:\\\\documents\\\\F盘\\\\pkg1\\\\pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盘\\pkg1\\pkgmoda.py

相对导入只搜索当前包路径，不搜索sys.path路径。

将pkg1\\pkgmoda.py剪切到“E**:**\\documents\\F盘”

# python2.7示例

E:\\documents\\F盘>d:\\Python27\\python
Python 2.7.18 (v2.7.18:8d21aa21f2, Apr 20 2020, 13:25:05) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg1.main_moda
run:E:\\documents\\F盘\\pkg1\\__init__.py
print(sys.path[0]):
# 只搜索包当前路径，不搜索sys.path路径
Traceback (most recent call last):
 File "", line 1, in 
 File "pkg1\\main_moda.py", line 5, in 
   from . import pkgmoda
ImportError: cannot import name pkgmoda
# python3.7示例

E:\\documents\\F盘>d:\\python3\\python
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 pkg1.main_moda
run:E:\\documents\\F盘\\pkg1\\__init__.py
print(sys.path[0]):
# 只搜索包当前路径，不搜索sys.path路径
Traceback (most recent call last):
 File "", line 1, in 
 File "E:\\documents\\F盘\\pkg1\\main_moda.py", line 5, in 
   from . import pkgmoda
ImportError: cannot import name 'pkgmoda' from 'pkg1' (E:\\documents\\F盘\\pkg1\\__init__.py)