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I have a custom QWidget that I have embedded into a QTableWidget.
When I toggle the QCheckBoxes and modify the text in the QLineEdit widgets, the program is not able to distinguish the widgets in rows 2 and 1 from the widgets in row 0. How can I change the program so that it prints the correct row and column of the QLineEdit widget that is being edited or the Checkbox that is being toggled?
Figure 1 shows a screenshot of the program with the output after selecting the third checkbox many times in Visual Studio Code. The output is expected to read “2 0” repeatedly but instead it reads “0 0”.
Figure 2 Similarly, when I modify the text in the QLineEdit in cell 2,0 from “My Custom Text” to “Text” the program prints “Handle Cell Edited 0,0”, although it is expected to print “Handle Cell Edited 2,0 Cell 2,0 was changed to Text”.
Code:
# Much of this code is copy pasted form user: three_pineapples post on stackoverflow:
# https://stackoverflow.com/a/26311179/18914416
import sys
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QWidget, QHBoxLayout, QTableWidget, \
QApplication, QTableWidgetItem, QLineEdit, QCheckBox
from PyQt5 import QtGui
class SimpleTable(QTableWidget):
def __init__(self,window):
# Call the parent constructor
QTableWidget.__init__(self)
self.window = window
class myWidget(QWidget):
#This code is adapted paritally form a post by user sebastian at:
#https://stackoverflow.com/a/29764770/18914416
def __init__(self,parent=None):
super(myWidget,self).__init__()
self.Layout1 = QHBoxLayout()
self.item = QLineEdit("My custom text")
#https://stackabuse.com/working-with-pythons-pyqt-framework/
self.Checkbox = QCheckBox()
self.Checkbox.setCheckState(Qt.CheckState.Unchecked)
self.Layout1.addWidget(self.Checkbox)
self.Layout1.addWidget(self.item)
#https://stackoverflow.com/questions/29764395/adding-multiple-widgets-to-qtablewidget-cell-in-pyqt
self.item.home(True)
#https://www.qtcentre.org/threads/58387-Left-text-alignment-for-long-text-on-QLineEdit
self.setLayout(self.Layout1)
class Window(QWidget):
def __init__(self):
super(Window, self).__init__()
layout = QHBoxLayout()
self.setLayout(layout)
self.table_widget = SimpleTable(window=self)
layout.addWidget(self.table_widget)
self.table_widget.setColumnCount(3)
self.table_widget.setHorizontalHeaderLabels(['Colour', 'Model'])
items = [('Red', 'Toyota'), ('Blue', 'RV'), ('Green', 'Beetle')]
for i in range(len(items)):
c = QTableWidgetItem(items[i][0])
m = QTableWidgetItem(items[i][1])
self.table_widget.insertRow(self.table_widget.rowCount())
self.table_widget.setItem(i, 1, c)
self.table_widget.setItem(i, 2, m)
myWidget1 = myWidget()
myWidget1.Checkbox.stateChanged.connect(self.handleButtonClicked)
myWidget1.item.editingFinished.connect(self.handle_cell_edited)
self.table_widget.setCellWidget(i,0,myWidget1)
myWidget1.Layout1.setContentsMargins(50*i+10,0,0,0)
self.show()
self.table_widget.itemChanged.connect(self.handle_cell_edited)
def handleButtonClicked(self):
#Adapted from a post by user: Andy at:
# https://stackoverflow.com/a/24149478/18914416
button = QApplication.focusWidget()
# or button = self.sender()
index = self.table_widget.indexAt(button.pos())
if index.isValid():
print(index.row(), index.column())
# I added this fuction:
def handle_cell_edited(self):
if QApplication.focusWidget() != None:
index = self.table_widget.indexAt(QApplication.focusWidget().pos())
x,y = index.column(),index.row()
if index.isValid():
print("Handle Cell Edited",index.row(), index.column())
if self.table_widget.item(y,x)!= None:
print(f"Cell {x},{y} was changed to {self.table_widget.item(y,x).text()}.")
def main():
app = QApplication(sys.argv)
window = Window()
sys.exit(app.exec_())
main()
What I've Tried So Far:
I learned that QT has two types of widgets that can be embedded in a table; a QTableWigetItem which can be inserted into a table using setItem()(3) and Qwidgets, which can be placed into a table using setCellWidget().(4) Generally, I know that using a QTableWigetItem one can set the item.setFlags(Qt.ItemFlag.ItemIsUserCheckable)
flag to create a checkbox in the cell. (3) However, when using the QTableWigetItem, I wasn’t able to find a way to indent the checkboxes. Because giving each checkbox its own indentation level is important in the context of my program, I’ve decided to use Qwidgets instead of QTableWigetItems in the few select cells where indenting is important.
I’ve read that by creating a QItemDelegate(5)(6), you can do a lot more with setting QWidgets in boxes. However, creating a delegate seems complicated, so I’d prefer to avoid this if possible. If there is no other way to make the program register the correct cell number of the cell being edited, creating a delegate will be the next thing I look into.
For anyone who might want to experiment with QTableWigetItems in this application, here is an equivalent program that uses QTableWigetItems instead of QWidgets but doesn't permit separate indentation or editing of the text field in column 0. For either and both of these two reasons, a QTableWigetItem seems not to be usable for the checkboxes in column 0.
Less Successful Attempt using QTableWidgetItem:
#Much of this code is copy pasted form user: three_pineapples post on stackoverflow:
# https://stackoverflow.com/a/26311179/18914416
import sys
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QWidget, QHBoxLayout, QTableWidget, \
QApplication, QTableWidgetItem, QLineEdit, QCheckBox
from PyQt5 import QtGui
class SimpleTable(QTableWidget):
def __init__(self,window):
QTableWidget.__init__(self)
self.window = window
class Window(QWidget):
def __init__(self):
super(Window, self).__init__()
layout = QHBoxLayout()
self.setLayout(layout)
self.table_widget = SimpleTable(window=self)
layout.addWidget(self.table_widget)
self.table_widget.setColumnCount(3)
self.table_widget.setHorizontalHeaderLabels(['Colour', 'Model'])
items = [('Red', 'Toyota'), ('Blue', 'RV'), ('Green', 'Beetle')]
for i in range(len(items)):
c = QTableWidgetItem(items[i][0])
m = QTableWidgetItem(items[i][1])
self.table_widget.insertRow(self.table_widget.rowCount())
self.table_widget.setItem(i, 1, c)
self.table_widget.setItem(i, 2, m)
item = QTableWidgetItem("My Custom Text")
item.setFlags(Qt.ItemFlag.ItemIsUserCheckable| Qt.ItemFlag.ItemIsEnabled)
item.setCheckState(Qt.CheckState.Unchecked)
self.table_widget.setItem(i,0,item)
#https://youtu.be/DM8Ryoot7MI?t=251
self.show()
#I added this line:
self.table_widget.itemChanged.connect(self.handle_cell_edited)
def handleButtonClicked(self):
#Adapted from a post by user: Andy at:
# https://stackoverflow.com/a/24149478/18914416
button = QApplication.focusWidget()
# or button = self.sender()
index = self.table_widget.indexAt(button.pos())
if index.isValid():
print(index.row(), index.column())
# I added this fuction:
def handle_cell_edited(self):
if QApplication.focusWidget() != None:
index = self.table_widget.indexAt(QApplication.focusWidget().pos())
x,y = index.column(),index.row()
if index.isValid():
print("Handle Cell Edited",index.row(), index.column())
if self.table_widget.item(y,x)!= None:
print(f"Cell {x},{y} was changed to {self.table_widget.item(y,x).text()}.")
def main():
app = QApplication(sys.argv)
window = Window()
sys.exit(app.exec_())
main()
Bibliography:
1.https://i.stack.imgur.com/FudE3.png
2.https://i.stack.imgur.com/C2ypp.png
3.https://youtu.be/DM8Ryoot7MI?t=251
4.https://stackoverflow.com/questions/24148968/how-to-add-multiple-qpushbuttons-to-a-qtableview/24149478#24149478
5.Creating a QItemDelegate for QWidgets, https://stackoverflow.com/a/35418141/18914416
6.Need to create a QItemDelegate to add a stylesheet to QTableWidgetItems: https://forum.qt.io/topic/13124/solved-qtablewidgetitem-set-stylesheet
The geometry of a widget is always relative to its parent.
In your first example, the problem is that the pos() returned for the widget is relative to the myWidget container, and since the vertical position is always a few pixels below the top of the parent (the layout margin), you always get the same value.
The second example has another conceptual problem: the checkbox of a checkable item is not an actual widget, so the widget you get is the table itself.
def handle_cell_edited(self):
# this will print True
print(isinstance(QApplication.focusWidget(), QTableWidget))
As explained above, the geometry is always relative to the parent, so you will actually get the position of the table relative to the window.
The solution to the first case is quite simple, as soon as you understand the relativity of coordinate systems. Note that you shall not rely on the focusWidget() (the widget might not accept focus), but actually get the sender(), which is the object that emitted the signal:
def handleButtonClicked(self):
sender = self.sender()
if not self.table_widget.isAncestorOf(sender):
return
# the widget coordinates must *always* be mapped to the viewport
# of the table, as the headers add margins
pos = sender.mapTo(self.table_widget.viewport(), QPoint())
index = self.table_widget.indexAt(pos)
if index.isValid():
print(index.row(), index.column())
In reality, this might not be that necessary, as an item delegate will suffice if the indentation is the only requirement: the solution is to properly set the option.rect() within initStyleOption() and use a custom role for the indentation:
IndentRole = Qt.UserRole + 1
class IndentDelegate(QStyledItemDelegate):
def initStyleOption(self, opt, index):
super().initStyleOption(opt, index)
indent = index.data(IndentRole)
if indent is not None:
left = min(opt.rect.right(),
opt.rect.x() + indent)
opt.rect.setLeft(left)
class SimpleTable(QTableWidget):
def __init__(self,window):
QTableWidget.__init__(self)
self.window = window
self.setItemDelegateForColumn(0, IndentDelegate(self))
class Window(QWidget):
def __init__(self):
# ...
for i in range(len(items)):
# ...
item.setData(IndentRole, 20 * i)
Using QtDesigner and PyQt5 with pyuic5 I'm setting up a FormLayout with a variable number of rows.
Each row is a custom widget created in QtDesigner, consisting of a QLabel and a QHBoxLayout containing a QLineEdit and QPushButton.
I create the row UI using
def get_data_widget(parent=None, **kwargs):
widget = QtWidgets.QWidget(parent)
dlg_ui = wgtDataRow.Ui_Form() # from the custom made widget
dlg_ui.setupUi(widget)
# recursively ensure all objectName()s are unique
rename_widget(widget, "_%s" % unique_id())
dlg_ui.label.setText(kwargs.get('name') or '')
dlg_ui.editData.setText(kwargs.get('value') or '')
return dlg_ui
The row UI is inserted in the QFormLayout in a QDialog method:
def add_data_entry_row(self, name, **kwargs):
# simplified code, but this is the bit that affects the QFormLayout
posn = kwargs.get('position', 0)
data_ui = get_data_widget(self, name=name, value=kwargs.get('value'))
self.dlg_ui.formLayout.insertRow(posn, data_ui.label, data_ui.widget)
The problem I have is that the first row of the QFormLayout is not responding to the mouse clicks.
If I insert a new row at 0 the previously unresponsive row is moved down and becomes responsive and the new (top) row unresponsive.
Can anyone throw any light on this?
While trying to generate a minimal example which had the same problem I found the cause. Basically I was making changes to the UI before executing show()
What I had (code minimised for clarity)
class Dialog(QtWidgets.QDialog):
def __init__(self, **kwargs):
super().__init__()
self.dlg_ui = Ui_Dialog()
self.dlg_ui.setupUi(self)
self.setModal(True)
self.init_ui(**kwargs) # load the UI widgets with data
self.show()
which should have been
class Dialog(QtWidgets.QDialog):
def __init__(self, **kwargs):
super().__init__()
self.dlg_ui = Ui_Dialog()
self.dlg_ui.setupUi(self)
self.setModal(True)
self.show() # excute BEFORE loading the UI
self.init_ui(**kwargs) # load the UI widgets with data
Using the code from Here and There, I made a GUI presenting my project on a smaller scale.
I have a qTableView,containing a large array of rows, and on each rows I have a delete and an edit button. On click, it should either edit or delete the current row. When using only the first source, it works exactly as intended, but as soon as I handle the click outside of the buttons class, it stops working.
Everytime I try to edit or delete, the button that either self.sender() or QtWidgets.qApp.focusWidget() sees as the sender has the coordinates [0,0], even if it's absolutely not it's coordinates.
I have searched on various websites and can't find this precise question.
What am I doing wrong, and what could I do to solve this problem?
My code :
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import QFileDialog, QMessageBox
class EditButtonsWidget(QtWidgets.QWidget):
# Credit to : https://stackoverflow.com/a/29764914/13812144
def __init__(self, parent=None):
super(EditButtonsWidget,self).__init__(parent)
# add your buttons
layout = QtWidgets.QHBoxLayout()
# adjust spacings to your needs
layout.setContentsMargins(0,0,0,0)
layout.setSpacing(0)
self.editButton = QtWidgets.QPushButton('edit')
self.deleteButton = QtWidgets.QPushButton('del')
self.buttonRow = 0
# add your buttons
layout.addWidget(self.editButton)
layout.addWidget(self.deleteButton)
self.setLayout(layout)
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
QtWidgets.QMainWindow.__init__(self,parent)
self.table = QtWidgets.QTableWidget()
self.table.setColumnCount(3)
self.setCentralWidget(self.table)
data1 = ['row1','row2','row3','row4']
data2 = ['1','2.0','3.00000001','3.9999999']
self.table.setRowCount(4)
for index in range(4):
item1 = QtWidgets.QTableWidgetItem(data1[index])
self.table.setItem(index,0,item1)
item2 = QtWidgets.QTableWidgetItem(data2[index])
self.table.setItem(index,1,item2)
self.btn_sell = EditButtonsWidget()
self.btn_sell.editButton.clicked.connect(self.handleButtonClicked)
self.table.setCellWidget(index,2,self.btn_sell)
def handleButtonClicked(self):
#button = QtWidgets.qApp.focusWidget()
button = self.sender()
index = self.table.indexAt(button.pos())
if index.isValid():
print(index.row(), index.column())
if __name__ == "__main__":
import sys
app = QtWidgets.QApplication(sys.argv)
MainWindow = MainWindow()
MainWindow.show()
sys.exit(app.exec_())
The position must be of the widget that is set in the QTableWidget, not of one of its children.
In this case it is better to consider the EditButtonsWidget as a black box and expose the clicked signals of the buttons as new signals so that the sender is EditButtonsWidget and no longer the buttons:
class EditButtonsWidget(QtWidgets.QWidget):
edit_clicked = QtCore.pyqtSignal()
delete_clicked = QtCore.pyqtSignal()
def __init__(self, parent=None):
super(EditButtonsWidget,self).__init__(parent)
# add your buttons
layout = QtWidgets.QHBoxLayout(self)
# adjust spacings to your needs
layout.setContentsMargins(0,0,0,0)
layout.setSpacing(0)
self.editButton = QtWidgets.QPushButton('edit')
self.deleteButton = QtWidgets.QPushButton('del')
# add your buttons
layout.addWidget(self.editButton)
layout.addWidget(self.deleteButton)
self.editButton.clicked.connect(self.edit_clicked)
self.deleteButton.clicked.connect(self.delete_clicked)
for index in range(4):
item1 = QtWidgets.QTableWidgetItem(data1[index])
self.table.setItem(index,0,item1)
item2 = QtWidgets.QTableWidgetItem(data2[index])
self.table.setItem(index,1,item2)
self.btn_sell = EditButtonsWidget()
self.btn_sell.edit_clicked.connect(self.handleButtonClicked) # <---
self.table.setCellWidget(index,2,self.btn_sell)
Widget positions always use the parent's coordinate system as a reference.
In your case, the button is a child of EditButtonsWidget, and since it's also the first widget and the layout has no margins, the button is placed at 0, 0 in that coordinate reference system.
A theoretical solution to your problem would be to map the widget position to the actual widget you need a reference for, which is the viewport of the scroll area (the table):
def handleButtonClicked(self):
button = self.sender()
viewportPosition = button.mapTo(self.table.viewport(), QtCore.QPoint())
index = self.table.indexAt(viewportPosition)
if index.isValid():
print(index.row(), index.column())
The mapping is done using an empty QPoint, since the top-left corner of a widget is always 0, 0 in local coordinates.
While this works, it's not the most logic nor elegant or safest way to do so, as you should reference the actual index instaed.
A better solution would be to map the table index, use that as argument of the widget constructor, and send that index for a custom signal.
class EditButtonsWidget(QtWidgets.QWidget):
editClicked = QtCore.pyqtSignal(object)
def __init__(self, index):
super(EditButtonsWidget,self).__init__()
self.index = index
# ...
self.editButton.clicked.connect(lambda: self.editClicked.emit(index))
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
# ...
for index in range(4):
# ...
persistenIndex = QtCore.QPersistentModelIndex(
self.table.indexFromItem(item2))
self.btn_sell = EditButtonsWidget(persistenIndex)
self.btn_sell.editClicked.connect(self.handleButtonClicked)
self.table.setCellWidget(index,2,self.btn_sell)
def handleButtonClicked(self, index):
if index.isValid():
print(index.row(), index.column())
Note that I used a QPersistentModelIndex, which ensures that the model index coordinates are always consistent even if the model changes (by deleting/inserting items or moving them).
Also note that you cannot directly use a QPersistentModelIndex for most functions that take a normal QModelIndex as parameter; in case you need that, you can recreate a QModelIndex like this:
modelIndex = self.table.model().index(
persistentIndex.row(), persistentIndex.column())
I have created an item pipeline as an answer to this question.
It is supposed to create a new file for every page according to the page_no value set in the item. This works mostly fine.
The problem is with the last csv file generated by the pipeline/item exporter, page-10.csv.
The last 10 values are not exported, so the file stays empty.
What could be the reason for this behaviour?
pipelines.py
from scrapy.exporters import CsvItemExporter
class PerFilenameExportPipeline:
"""Distribute items across multiple CSV files according to their 'page_no' field"""
def open_spider(self, spider):
self.filename_to_exporter = {}
def spider_closed(self, spider):
for exporter in self.filename_to_exporter.values():
exporter.finish_exporting()
def _exporter_for_item(self, item):
filename = 'page-' + str(item['page_no'])
del item['page_no']
if filename not in self.filename_to_exporter:
f = open(f'{filename}.csv', 'wb')
exporter = CsvItemExporter(f, export_empty_fields=True)
exporter.start_exporting()
self.filename_to_exporter[filename] = exporter
return self.filename_to_exporter[filename]
def process_item(self, item, spider):
exporter = self._exporter_for_item(item)
exporter.export_item(item)
return item
spider
import scrapy
from ..pipelines import PerFilenameExportPipeline
class spidey(scrapy.Spider):
name = "idk"
custom_settings = {
'ITEM_PIPELINES': {
PerFilenameExportPipeline: 100
}
}
def start_requests(self):
yield scrapy.Request("http://quotes.toscrape.com/", cb_kwargs={'page_no': 1})
def parse(self, response, page_no):
for qts in response.xpath("//*[#class=\"quote\"]"):
yield {
'page_no': page_no,
'author' : qts.xpath("./span[2]/small/text()").get(),
'quote' : qts.xpath("./*[#class=\"text\"]/text()").get()
}
next_pg = response.xpath('//li[#class="next"]/a/#href').get()
if next_pg is not None:
yield response.follow(next_pg, cb_kwargs={'page_no': page_no + 1})
I know, 2 years later, but still - it might turn out helpful for someone.
It looks like you're never closing the file you're writing to (as you're using inline open). Please compare your code to the one in Scrapy's docs (the "Using Item Exporters" section): https://docs.scrapy.org/en/latest/topics/exporters.html
Besides, the method should now be called "close_spider", not "spider_closed"
Changing your code to the following should help:
from scrapy.exporters import CsvItemExporter
class PerFilenameExportPipeline:
def open_spider(self, spider):
self.filename_to_exporter = {}
def close_spider(self, spider):
#iterating over exporter-file tuples instead of only exporters
for exporter, csv_file in self.filename_to_exporter.values():
exporter.finish_exporting()
#closing the file
csv_file.close()
def _exporter_for_item(self, item):
filename = 'page-' + str(item['page_no'])
del item['page_no']
if filename not in self.filename_to_exporter:
csv_file = open(f'{filename}.csv', 'wb')
exporter = CsvItemExporter(f, export_empty_fields=True)
exporter.start_exporting()
#adding both exporter & file to later be closed as the dict's value
self.filename_to_exporter[filename] = (exporter, csv_file)
#picking only the exporter via [0]
return self.filename_to_exporter[filename][0]
def process_item(self, item, spider):
exporter = self._exporter_for_item(item)
exporter.export_item(item)
return item
I am currently following this tutorial on threading in PyQt (code from here). As it was written in PyQt4 (and Python2), I adapted the code to work with PyQt5 and Python3.
Here is the gui file (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"))
and the main script (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()
Now I'm getting the following error:
AttributeError: 'ThreadingTutorial' object has no attribute 'connect'
Can anyone please tell me how to fix this? Any help would be, as always, very much appreciated.
Using QObject.connect() and similar in PyQt4 is known as "Old style signals", and is not supported in PyQt5 anymore, it supports only "New style signals", which already in PyQt4 was the recommended way to connect signals.
In PyQt5 you need to use the connect() and emit() methods of the bound signal directly, e.g. instead of:
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)
use:
self.add_post.emit(top_post)
...
self.get_thread.add_post.connect(self.add_post)
self.get_thread.finished.connect(self.done)
However for this to work you need to explicitly define the add_post signal on your getPostsThread first, otherwise you'll get an attribute error.
class getPostsThread(QThread):
add_post = pyqtSignal(str)
...
In PyQt4 with old style signals when a signal was used it was automatically defined, this now needs to be done explicitly.