[Python] module & class

最近寫python遇到很笨的問題

$ vi serial.py

import serial
                                                  
ser = serial.Serial('/dev/ttyUSB0', 9600)
ser.write("hello world!")

錯誤訊息

Traceback (most recent call last):
  File "serial.py", line 1, in 
    import serial
  File "/home/user/python/serial.py", line 4, in 
    ser = serial.Serial('/dev/ttyUSB0', 9600)
AttributeError: 'module' object has no attribute 'Serial'

如果照stackoverflow的講法, 應該改為from serial import serial

#import serial                                                                   
from serial import serial

ser = serial.Serial('/dev/ttyUSB0', 9600)
ser.write("hello world!")

錯誤訊息

Traceback (most recent call last):
  File "serial.py", line 2, in 
    from serial import serial
  File "/home/user/python/serial.py", line 2, in 
    from serial import serial
ImportError: cannot import name serial

又有人說, 應該改為from serial import *

#import serial                                                                   
#from serial import serial
from serial import *

ser = serial.Serial('/dev/ttyUSB0', 9600)
ser.write("hello world!")

錯誤訊息

Traceback (most recent call last):
  File "serial.py", line 2, in 
    from serial import serial
  File "/home/user/python/serial.py", line 2, in 
    from serial import serial
ImportError: cannot import name serial

最後把檔名serial.py改掉, 隨便改成foo.py就可以了

import serial
                                                  
ser = serial.Serial('/dev/ttyUSB0', 9600)
ser.write("hello world!")

如果再改成

#import serial                                                                   
from serial import serial

ser = serial.Serial('/dev/ttyUSB0', 9600)
ser.write("hello world!")

錯誤訊息

Traceback (most recent call last):
  File "s.py", line 2, in 
    from serial import serial
ImportError: cannot import name serial

如果改回

#import serial
#from serial import serial
from serial import *

ser = serial.Serial('/dev/ttyUSB0', 9600)                                       
ser.write("hello world!")

錯誤訊息

Traceback (most recent call last):
  File "s.py", line 4, in 
    ser = serial.Serial('/dev/ttyUSB0', 9600)
NameError: name 'serial' is not defined

好吧, 我還沒搞懂python的語法就在亂搞了...