[FIXED] PyQt5 and subprocess.Popen(...)

Issue

I have 3 classes

One is the Console class:

class Console(QWidget):
    def __init__(self):
        super().__init__()
        self.editor = QPlainTextEdit(self)
        self.editor.setReadOnly(True)
        self.font = QFont()
        self.font.setFamily(editor["editorFont"])
        self.font.setPointSize(12)
        self.layout = QVBoxLayout()
        self.layout.addWidget(self.editor, 1)
        self.setLayout(self.layout)
        self.output = None
        self.error = None
        self.editor.setFont(self.font)

    def run(self, command):
        """Executes a system command."""

        out, err = subprocess.Popen(command, shell=True,    stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
        self.output = out
        self.error = err
        self.editor.setPlainText((self.output + self.error).decode())
        return self.output + self.error

The other one is a Tabs class which assigns Console() to the variable self.console.

And then I have the Main class which has a function called Terminal which can be called by a keyboard shortcut Shift+F10

That will take the current filename of the file opened (this is handled with the Tabs class) and run it using subprocess.

Now we get to the problem: when running some programs that aren't instant, the whole GUI freezes and I can't figure out how to make the GUI responsive when the Console class has executed the run function.

The whole code can be found here: https://github.com/Fuchsiaff/PyPad

Solution

You do not use subprocess.Popen() because it is blocking, and just one of the disadvantages of blocking tasks is that they do not allow the GUI to perform other jobs, for this Qt provides the QProcess class that does not block the event-loop:

import sys

from PyQt5 import QtCore, QtGui, QtWidgets

class Console(QtWidgets.QWidget):
    errorSignal = QtCore.pyqtSignal(str) 
    outputSignal = QtCore.pyqtSignal(str)
    def __init__(self):
        super().__init__()
        self.editor = QtWidgets.QPlainTextEdit(self)
        self.editor.setReadOnly(True)
        self.font = QtGui.QFont()
        # self.font.setFamily(editor["editorFont"])
        self.font.setPointSize(12)
        self.layout = QtWidgets.QVBoxLayout()
        self.layout.addWidget(self.editor, 1)
        self.setLayout(self.layout)
        self.output = None
        self.error = None
        self.editor.setFont(self.font)
        self.process = QtCore.QProcess()
        self.process.readyReadStandardError.connect(self.onReadyReadStandardError)
        self.process.readyReadStandardOutput.connect(self.onReadyReadStandardOutput)

    def onReadyReadStandardError(self):
        error = self.process.readAllStandardError().data().decode()
        self.editor.appendPlainText(error)
        self.errorSignal.emit(error)

    def onReadyReadStandardOutput(self):
        result = self.process.readAllStandardOutput().data().decode()
        self.editor.appendPlainText(result)
        self.outputSignal.emit(result)


    def run(self, command):
        """Executes a system command."""
        # clear previous text
        self.editor.clear()
        self.process.start(command)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    w = Console()
    w.show()
    w.errorSignal.connect(lambda error: print(error))
    w.outputSignal.connect(lambda output: print(output))
    w.run("ping 8.8.8.8 -c 100")
    sys.exit(app.exec_())

Answered By - eyllanesc