Python 2.7-类

Question

我正在尝试在python中编辑库(perfmon)-文件为session.py

我想添加一个模块，该模块可以记录来自USB端口的一些读数。

这也是我对python类的第一次尝试

from perfmon import *

import os

import sys

import serial

# Common base class

class Session:

  def __init__(self, events):

    self.system = System()

    self.event_names = events

    self.events = []

    self.fds = []

    for e in events:

      err, encoding = pfm_get_perf_event_encoding(e, PFM_PLM0 | PFM_PLM3,

                                                  None, None)

      self.events.append(encoding)

    self.USB = serial.Serial("/dev/ttyUSB0",115200)

  def __del__(self):

    pass

  def read(self, fd):

    # TODO: determine counter width

    return os.read(fd, 8)

class PerThreadSession(Session):

  def __init__(self, pid, events):

    self.pid = pid

    Session.__init__(self, events)

  def __del__(self):

    Session.__del__(self)

  def start(self):

    for e in self.events:

      self.fds.append(perf_event_open(e, self.pid, -1, -1, 0))

  def read(self, i):

    return Session.read(self, self.fds[i])

class USB(Session):

  def __init__(self):   

    return self.USB

这是我得到的以下错误：

Python 2.7.3 (default, Apr 14 2012, 08:58:41) [GCC] on linux2

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

>>> import perfmon

>>> test = perfmon.USB()

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

AttributeError: 'module' object has no attribute 'USB'

我在做什么错？我了解self在python中充当构造函数，我可以在其中返回值吗？

Answer 1

据我了解，在您的情况下，答案是>>> from perfmon import session>>> test = session.USB()但是这种方式，你的举动是错误的。您应该在工作区/项目目录中创建自己的模块。导入会话模块并在那里创建类from perfmon import sessionclass USB(Session):&nbsp; &nbsp; def __init__(self):&nbsp; &nbsp;&nbsp; &nbsp; &nbsp; &nbsp; pass #I have changed this part as It has two errors in your example

Answer 2

您不能从类构造函数返回任何内容（除None之外）。否则会得到TypeError:&nbsp;__init__()&nbsp;should&nbsp;return&nbsp;None