在pyqt中显示日志的最佳方法？

Question

我目前正在使用qt designer进行GUI。我想知道如何在GUI上打印字符串，就像记录器窗口一样。我正在使用pyqt5。

Answer 1

如果您使用Python logging模块可以轻松创建自定义日志记录处理程序，将日志消息传递到QPlainTextEdit实例（如Christopher所述）。

要做到这一点，你首先继承logging.Handler。在这个__init__中，我们创建了包含日志的QPlainTextEdit。这里的关键是句柄将通过emit()函数接收消息。所以我们重载这个函数并将消息文本传递给QPlainTextEdit。

import logging

class QPlainTextEditLogger(logging.Handler):
    def __init__(self, parent):
        super(Logger, self).__init__()

        self.widget = QPlainTextEdit(parent)
        self.widget.setReadOnly(True)

    def emit(self, record):
        msg = self.format(record)
        self.widget.textCursor().appendPlainText(msg)

    def write(self, m):
        pass

从此类创建一个对象，将其传递给QPlainTextEdit的父项（例如主窗口或布局）。然后，您可以为当前记录器添加此处理程序。

# Set up logging to use your widget as a handler
log_handler = QPlainTextEditLogger(<parent widget>)
logging.getLogger().addHandler(log_handler)

Answer 2

改编自Todd Vanyo的PyQt5示例：

import sys
from PyQt5 import QtWidgets
import logging

# Uncomment below for terminal log messages
# logging.basicConfig(level=logging.DEBUG, format=' %(asctime)s - %(name)s - %(levelname)s - %(message)s')

class QTextEditLogger(logging.Handler):
    def __init__(self, parent):
        super().__init__()
        self.widget = QtWidgets.QPlainTextEdit(parent)
        self.widget.setReadOnly(True)

    def emit(self, record):
        msg = self.format(record)
        self.widget.appendPlainText(msg)


class MyDialog(QtWidgets.QDialog, QtWidgets.QPlainTextEdit):
    def __init__(self, parent=None):
        super().__init__(parent)

        logTextBox = QTextEditLogger(self)
        # You can format what is printed to text box
        logTextBox.setFormatter(logging.Formatter('%(asctime)s - %(levelname)s - %(message)s'))
        logging.getLogger().addHandler(logTextBox)
        # You can control the logging level
        logging.getLogger().setLevel(logging.DEBUG)

        self._button = QtWidgets.QPushButton(self)
        self._button.setText('Test Me')

        layout = QtWidgets.QVBoxLayout()
        # Add the new logging box widget to the layout
        layout.addWidget(logTextBox.widget)
        layout.addWidget(self._button)
        self.setLayout(layout)

        # Connect signal to slot
        self._button.clicked.connect(self.test)

    def test(self):
        logging.debug('damn, a bug')
        logging.info('something to remember')
        logging.warning('that\'s not right')
        logging.error('foobar')

app = QtWidgets.QApplication(sys.argv)
dlg = MyDialog()
dlg.show()
dlg.raise_()
sys.exit(app.exec_())

Answer 3

这是一个基于mfitzp's answer的完整工作示例：

import sys
from PyQt4 import QtCore, QtGui
import logging

# Uncomment below for terminal log messages
# logging.basicConfig(level=logging.DEBUG, format=' %(asctime)s - %(name)s - %(levelname)s - %(message)s')    

class QPlainTextEditLogger(logging.Handler):
    def __init__(self, parent):
        super().__init__()
        self.widget = QtGui.QPlainTextEdit(parent)
        self.widget.setReadOnly(True)    

    def emit(self, record):
        msg = self.format(record)
        self.widget.appendPlainText(msg)    


class MyDialog(QtGui.QDialog, QPlainTextEditLogger):
    def __init__(self, parent=None):
        super().__init__(parent)    

        logTextBox = QPlainTextEditLogger(self)
        # You can format what is printed to text box
        logTextBox.setFormatter(logging.Formatter('%(asctime)s - %(levelname)s - %(message)s'))
        logging.getLogger().addHandler(logTextBox)
        # You can control the logging level
        logging.getLogger().setLevel(logging.DEBUG)

        self._button = QtGui.QPushButton(self)
        self._button.setText('Test Me')    

        layout = QtGui.QVBoxLayout()
        # Add the new logging box widget to the layout
        layout.addWidget(logTextBox.widget)
        layout.addWidget(self._button)
        self.setLayout(layout)    

        # Connect signal to slot
        self._button.clicked.connect(self.test)    

    def test(self):
        logging.debug('damn, a bug')
        logging.info('something to remember')
        logging.warning('that\'s not right')
        logging.error('foobar')

if (__name__ == '__main__'):
    app = None
    if (not QtGui.QApplication.instance()):
        app = QtGui.QApplication([])
    dlg = MyDialog()
    dlg.show()
    dlg.raise_()
    if (app):
        app.exec_()

Answer 4

听起来你想要将QPlainTextEdit小部件设置为只读。

考虑将背景颜色更改为灰色，以便为用户提供不可编辑的提示。如果您希望它可滚动或文本可选，也由您决定。

This answer可以让你开始子类化QPlainTextEdit来滚动输出，保存到文件，无论如何。

Answer 5

Alex的答案在单线程场景中应该没问题，但如果您正在登录另一个线程（QThread），您可能会收到以下警告：

QObject::connect: Cannot queue arguments of type 'QTextCursor'
(Make sure 'QTextCursor' is registered using qRegisterMetaType().)

这是因为您在不使用Qt信号/插槽机制的情况下从主线程以外的线程修改GUI（self.widget.appendPlainText(msg)）。

这是我的解决方案：

# my_logger.py

import logging
from PyQt5.QtCore import pyqtSignal, QObject

class Handler(QObject, logging.Handler):
    new_record = pyqtSignal(object)

    def __init__(self, parent):
        super().__init__(parent)
        super(logging.Handler).__init__()
        formatter = Formatter('%(asctime)s|%(levelname)s|%(message)s|', '%d/%m/%Y %H:%M:%S')
        self.setFormatter(formatter)

    def emit(self, record):
        msg = self.format(record)
        self.new_record.emit(msg) # <---- emit signal here

class Formatter(logging.Formatter):
    def formatException(self, ei):
        result = super(Formatter, self).formatException(ei)
        return result

    def format(self, record):
        s = super(Formatter, self).format(record)
        if record.exc_text:
            s = s.replace('\n', '')
        return s

   # gui.py

   ... # GUI code
   ...
   def setup_logger(self)
        handler = Handler(self)
        log_text_box = QPlainTextEdit(self)
        self.main_layout.addWidget(log_text_box)
        logging.getLogger().addHandler(handler)
        logging.getLogger().setLevel(logging.INFO)
        handler.new_record.connect(log_text_box.appendPlainText) # <---- connect QPlainTextEdit.appendPlainText slot
   ...