我目前正在关注PyQt中的线程this教程（来自here的代码）。由于它是用PyQt4（和Python2）编写的，我调整了代码以使用PyQt5和Python3。
这是gui文件（newdesign.py）：
# -*- coding: utf-8 -*-
# Form implementation generated from reading ui file 'threading_design.ui'
#
# Created by: PyQt5 UI code generator 5.6
#
# WARNING! All changes made in this file will be lost!
from PyQt5 import QtCore, QtGui, QtWidgets
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.setObjectName("MainWindow")
MainWindow.resize(526, 373)
self.centralwidget = QtWidgets.QWidget(MainWindow)
self.centralwidget.setObjectName("centralwidget")
self.verticalLayout = QtWidgets.QVBoxLayout(self.centralwidget)
self.verticalLayout.setObjectName("verticalLayout")
self.subreddits_input_layout = QtWidgets.QHBoxLayout()
self.subreddits_input_layout.setObjectName("subreddits_input_layout")
self.label_subreddits = QtWidgets.QLabel(self.centralwidget)
self.label_subreddits.setObjectName("label_subreddits")
self.subreddits_input_layout.addWidget(self.label_subreddits)
self.edit_subreddits = QtWidgets.QLineEdit(self.centralwidget)
self.edit_subreddits.setObjectName("edit_subreddits")
self.subreddits_input_layout.addWidget(self.edit_subreddits)
self.verticalLayout.addLayout(self.subreddits_input_layout)
self.label_submissions_list = QtWidgets.QLabel(self.centralwidget)
self.label_submissions_list.setObjectName("label_submissions_list")
self.verticalLayout.addWidget(self.label_submissions_list)
self.list_submissions = QtWidgets.QListWidget(self.centralwidget)
self.list_submissions.setBatchSize(1)
self.list_submissions.setObjectName("list_submissions")
self.verticalLayout.addWidget(self.list_submissions)
self.progress_bar = QtWidgets.QProgressBar(self.centralwidget)
self.progress_bar.setProperty("value", 0)
self.progress_bar.setObjectName("progress_bar")
self.verticalLayout.addWidget(self.progress_bar)
self.buttons_layout = QtWidgets.QHBoxLayout()
self.buttons_layout.setObjectName("buttons_layout")
self.btn_stop = QtWidgets.QPushButton(self.centralwidget)
self.btn_stop.setEnabled(False)
self.btn_stop.setObjectName("btn_stop")
self.buttons_layout.addWidget(self.btn_stop)
self.btn_start = QtWidgets.QPushButton(self.centralwidget)
self.btn_start.setObjectName("btn_start")
self.buttons_layout.addWidget(self.btn_start)
self.verticalLayout.addLayout(self.buttons_layout)
MainWindow.setCentralWidget(self.centralwidget)
self.retranslateUi(MainWindow)
QtCore.QMetaObject.connectSlotsByName(MainWindow)
def retranslateUi(self, MainWindow):
_translate = QtCore.QCoreApplication.translate
MainWindow.setWindowTitle(_translate("MainWindow", "Threading Tutorial - nikolak.com "))
self.label_subreddits.setText(_translate("MainWindow", "Subreddits:"))
self.edit_subreddits.setPlaceholderText(_translate("MainWindow", "python,programming,linux,etc (comma separated)"))
self.label_submissions_list.setText(_translate("MainWindow", "Submissions:"))
self.btn_stop.setText(_translate("MainWindow", "Stop"))
self.btn_start.setText(_translate("MainWindow", "Start"))
和主要脚本（main.py）：
from PyQt5 import QtWidgets
from PyQt5.QtCore import QThread, pyqtSignal, QObject
import sys
import newdesign
import urllib.request
import json
import time
class getPostsThread(QThread):
def __init__(self, subreddits):
"""
Make a new thread instance with the specified
subreddits as the first argument. The subreddits argument
will be stored in an instance variable called subreddits
which then can be accessed by all other class instance functions
:param subreddits: A list of subreddit names
:type subreddits: list
"""
QThread.__init__(self)
self.subreddits = subreddits
def __del__(self):
self.wait()
def _get_top_post(self, subreddit):
"""
Return a pre-formatted string with top post title, author,
and subreddit name from the subreddit passed as the only required
argument.
:param subreddit: A valid subreddit name
:type subreddit: str
:return: A string with top post title, author,
and subreddit name from that subreddit.
:rtype: str
"""
url = "https://www.reddit.com/r/{}.json?limit=1".format(subreddit)
headers = {'User-Agent': 'nikolak@outlook.com tutorial code'}
request = urllib.request.Request(url, header=headers)
response = urllib.request.urlopen(request)
data = json.load(response)
top_post = data['data']['children'][0]['data']
return "'{title}' by {author} in {subreddit}".format(**top_post)
def run(self):
"""
Go over every item in the self.subreddits list
(which was supplied during __init__)
and for every item assume it's a string with valid subreddit
name and fetch the top post using the _get_top_post method
from reddit. Store the result in a local variable named
top_post and then emit a pyqtSignal add_post(QString) where
QString is equal to the top_post variable that was set by the
_get_top_post function.
"""
for subreddit in self.subreddits:
top_post = self._get_top_post(subreddit)
self.emit(pyqtSignal('add_post(QString)'), top_post)
self.sleep(2)
class ThreadingTutorial(QtWidgets.QMainWindow, newdesign.Ui_MainWindow):
"""
How the basic structure of PyQt GUI code looks and behaves like is
explained in this tutorial
http://nikolak.com/pyqt-qt-designer-getting-started/
"""
def __init__(self):
super(self.__class__, self).__init__()
self.setupUi(self)
self.btn_start.clicked.connect(self.start_getting_top_posts)
def start_getting_top_posts(self):
# Get the subreddits user entered into an QLineEdit field
# this will be equal to '' if there is no text entered
subreddit_list = str(self.edit_subreddits.text()).split(',')
if subreddit_list == ['']: # since ''.split(',') == [''] we use that to check
# whether there is anything there to fetch from
# and if not show a message and abort
QtWidgets.QMessageBox.critical(self, "No subreddits",
"You didn't enter any subreddits.",
QtWidgets.QMessageBox.Ok)
return
# Set the maximum value of progress bar, can be any int and it will
# be automatically converted to x/100% values
# e.g. max_value = 3, current_value = 1, the progress bar will show 33%
self.progress_bar.setMaximum(len(subreddit_list))
# Setting the value on every run to 0
self.progress_bar.setValue(0)
# We have a list of subreddits which we use to create a new getPostsThread
# instance and we pass that list to the thread
self.get_thread = getPostsThread(subreddit_list)
# Next we need to connect the events from that thread to functions we want
# to be run when those pyqtSignals get fired
# Adding post will be handeled in the add_post method and the pyqtSignal that
# the thread will emit is pyqtSignal("add_post(QString)")
# the rest is same as we can use to connect any pyqtSignal
self.connect(self.get_thread, pyqtSignal("add_post(QString)"), self.add_post)
# This is pretty self explanatory
# regardless of whether the thread finishes or the user terminates it
# we want to show the notification to the user that adding is done
# and regardless of whether it was terminated or finished by itself
# the finished pyqtSignal will go off. So we don't need to catch the
# terminated one specifically, but we could if we wanted.
self.connect(self.get_thread, pyqtSignal("finished()"), self.done)
# We have all the events we need connected we can start the thread
self.get_thread.start()
# At this point we want to allow user to stop/terminate the thread
# so we enable that button
self.btn_stop.setEnabled(True)
# And we connect the click of that button to the built in
# terminate method that all QThread instances have
self.btn_stop.clicked.connect(self.get_thread.terminate)
# We don't want to enable user to start another thread while this one is
# running so we disable the start button.
self.btn_start.setEnabled(False)
def add_post(self, post_text):
"""
Add the text that's given to this function to the
list_submissions QListWidget we have in our GUI and
increase the current value of progress bar by 1
:param post_text: text of the item to add to the list
:type post_text: str
"""
self.list_submissions.addItem(post_text)
self.progress_bar.setValue(self.progress_bar.value()+1)
def done(self):
"""
Show the message that fetching posts is done.
Disable Stop button, enable the Start one and reset progress bar to 0
"""
self.btn_stop.setEnabled(False)
self.btn_start.setEnabled(True)
self.progress_bar.setValue(0)
QtWidgets.QMessageBox.information(self, "Done!", "Done fetching posts!")
def main():
app = QtWidgets.QApplication(sys.argv)
form = ThreadingTutorial()
form.show()
app.exec_()
if __name__ == '__main__':
main()
现在我收到以下错误：
AttributeError: 'ThreadingTutorial' object has no attribute 'connect'
任何人都可以告诉我如何解决这个问题？一如既往，非常感谢任何帮助。
答案 0 :(得分：8)
在PyQt4中使用QObject.connect()和类似物被称为“旧式信号”和is not supported in PyQt5，它只支持"New style signals"，已经在PyQt4中建议连接信号的方法
在PyQt5中，您需要直接使用绑定信号的connect()和emit()方法，例如而不是：
self.emit(pyqtSignal('add_post(QString)'), top_post)
...
self.connect(self.get_thread, pyqtSignal("add_post(QString)"), self.add_post)
self.connect(self.get_thread, pyqtSignal("finished()"), self.done)
使用：
self.add_post.emit(top_post)
...
self.get_thread.add_post.connect(self.add_post)
self.get_thread.finished.connect(self.done)
但要实现此目的，您需要先在add_post上明确定义getPostsThread信号，否则会出现属性错误。
class getPostsThread(QThread):
add_post = pyqtSignal(str)
...
在PyQt4中，当使用信号时，旧样式信号是automatically defined，现在需要明确地完成。