python包模塊相對導入from和import介紹2

3.5.3 示例import-python2.7搜索當前包

python2.7先搜索當前包目錄，再搜索sys.path模塊搜索路徑。即先相對再絕對。

本示例在交互模式執(zhí)行，非文件模式執(zhí)行。

E**:**\\documents\\F盤\\ 目錄不存在pkgmoda.py文件

# 打開cmd，執(zhí)行下面命令
E:\\documents\\F盤>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盤\\pkg1\\__init__.pyc
print(sys.path[0]):
run:E:\\documents\\F盤\\pkg1\\pkgmoda.pyc
print(string):<module 'string' from 'd:\\Python27\\lib\\string.pyc'>
run:E:\\documents\\F盤\\pkg1\\main_moda.pyc
# 先搜索當前包目錄
print(pkgmoda):<module 'pkg1.pkgmoda' from 'pkg1\\pkgmoda.pyc'>
pkgmoda.index:E:\\documents\\F盤\\pkg1\\pkgmoda.pyc

3.5.4 示例import-python3.7略過當前包

python3.7不搜索當前包目錄，直接搜索sys.path模塊搜索路徑，即絕對導入。

本示例在交互模式執(zhí)行，非文件模式執(zhí)行。

E**:**\\documents\\F盤\\ 目錄不存在pkgmoda.py文件

# 打開cmd，執(zhí)行下面命令
E:\\documents\\F盤>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盤\\pkg1\\__init__.py
print(sys.path[0]):
# 不搜索當前包目錄
Traceback (most recent call last):
 File "", line 1, in 
 File "E:\\documents\\F盤\\pkg1\\main_moda.py", line 4, in 
   import pkgmoda
ModuleNotFoundError: No module named 'pkgmoda'

3.5.5 示例import-python3.7程序目錄-文件模式

python3.7直接搜索sys.path模塊搜索路徑，即絕對導入。

本示例在文件模式執(zhí)行，非交互模式執(zhí)行。

E**:**\\documents\\F盤\\ 目錄不存在pkgmoda.py文件

# 打開cmd，執(zhí)行下面命令
E:\\documents\\F盤>d:\\python3\\python pkg1\\main_moda.py
# 程序目錄為 pkg1
print(sys.path[0]):E:\\documents\\F盤\\pkg1
run:E:\\documents\\F盤\\pkg1\\pkgmoda.py
print(string):<module 'string' from 'd:\\\\python3\\\\lib\\\\string.py'>
run:E:\\documents\\F盤\\pkg1\\main_moda.py
# 搜索sys.path的程序目錄
print(pkgmoda):<module 'pkgmoda' from 'E:\\\\documents\\\\F盤\\\\pkg1\\\\pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盤\\pkg1\\pkgmoda.py

3.5.6 示例import-sys.path

將pkg1\\pkgmoda.py剪切到“E**:**\\documents\\F盤”。

當前包目錄沒有模塊，sys.path的程序目錄有模塊。

python2.7先當前包目錄，在sys.path，

python3.7只sys.path。

本示例在交互模式執(zhí)行，非文件模式執(zhí)行。

# python2.7示例
E:\\documents\\F盤>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盤\\pkg1\\__init__.pyc
print(sys.path[0]):
run:E:\\documents\\F盤\\pkgmoda.py
print(string):<module 'string' from 'd:\\Python27\\lib\\string.pyc'>
run:E:\\documents\\F盤\\pkg1\\main_moda.py
# 搜索程序目錄
print(pkgmoda):<module 'pkgmoda' from 'pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盤\\pkgmoda.py
# python3.7示例
E:\\documents\\F盤>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盤\\pkg1\\__init__.py
print(sys.path[0]):
run:E:\\documents\\F盤\\pkgmoda.py
print(string):<module 'string' from 'd:\\\\python3\\\\lib\\\\string.py'>
run:E:\\documents\\F盤\\pkg1\\main_moda.py
# 搜索程序目錄
print(pkgmoda):<module 'pkgmoda' from 'E:\\\\documents\\\\F盤\\\\pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盤\\pkgmoda.py

3.5.7 示例from點相對導入

“目錄文件內(nèi)容-1”修改 main_moda.py 為相對導入 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))

本示例在交互模式執(zhí)行，非文件模式執(zhí)行。

E**:**\\documents\\F盤\\ 目錄不存在pkgmoda.py文件

相對導入from . import module 從當前包搜索。

# python2.7示例
E:\\documents\\F盤>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盤\\pkg1\\__init__.py
print(sys.path[0]):
run:E:\\documents\\F盤\\pkg1\\pkgmoda.py
print(string):<module 'string' from 'd:\\Python27\\lib\\string.pyc'>
run:E:\\documents\\F盤\\pkg1\\main_moda.py
# python2.7 相對導入從當前包搜索
print(pkgmoda):<module 'pkg1.pkgmoda' from 'pkg1\\pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盤\\pkg1\\pkgmoda.py

# python3.7示例
E:\\documents\\F盤>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盤\\pkg1\\__init__.py
print(sys.path[0]):
run:E:\\documents\\F盤\\pkg1\\pkgmoda.py
print(string):<module 'string' from 'd:\\\\python3\\\\lib\\\\string.py'>
run:E:\\documents\\F盤\\pkg1\\main_moda.py
# python3.7 相對導入從當前包搜索
print(pkgmoda):<module 'pkg1.pkgmoda' from 'E:\\\\documents\\\\F盤\\\\pkg1\\\\pkgmoda.py'>
pkgmoda.index:E:\\documents\\F盤\\pkg1\\pkgmoda.py

相對導入只搜索當前包路徑，不搜索sys.path路徑。

將pkg1\\pkgmoda.py剪切到“E**:**\\documents\\F盤”

# python2.7示例

E:\\documents\\F盤>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盤\\pkg1\\__init__.py
print(sys.path[0]):
# 只搜索包當前路徑，不搜索sys.path路徑
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盤>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盤\\pkg1\\__init__.py
print(sys.path[0]):
# 只搜索包當前路徑，不搜索sys.path路徑
Traceback (most recent call last):
 File "", line 1, in 
 File "E:\\documents\\F盤\\pkg1\\main_moda.py", line 5, in 
   from . import pkgmoda
ImportError: cannot import name 'pkgmoda' from 'pkg1' (E:\\documents\\F盤\\pkg1\\__init__.py)