Python 在pyqt中显示日志的最佳方式？

Best way to display logs in pyqt?

提问by Carlo Angelo

I am currently working on a GUI using qt designer. I am wondering how I should go about printing strings on the GUI that acts like a logger window. I am using pyqt5.

我目前正在使用 qt 设计器开发 GUI。我想知道我应该如何在像记录器窗口一样的 GUI 上打印字符串。我正在使用 pyqt5。

回答by Christopher Peterson

Sounds like you'll want to use a QPlainTextEditwidget set to read-only.

听起来您想使用设置为只读的QPlainTextEdit小部件。

Consider changing the background color to gray to give the user a hint that it is not editable. It is also up to you if you want it to be scrollable or the text selectable.

考虑将背景颜色更改为灰色，以提示用户它不可编辑。如果您希望它可滚动或可选择文本，这也取决于您。

This answercan get you started subclassing QPlainTextEdit to scroll with output, save to a file, whatever.

这个答案可以让你开始继承 QPlainTextEdit 以滚动输出，保存到文件，等等。

回答by mfitzp

If you are using the Python loggingmodule to can easily create a custom logging handler that passes the log messages through to a QPlainTextEditinstance (as described by Christopher).

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

To do this you first subclass logging.Handler. In this __init__we create the QPlainTextEditthat will contain the logs. The key bit here is that the handle will be receiving messages via the emit()function. So we overload this function and pass the message text into the QPlainTextEdit.

为此，您首先要子类化logging.Handler. 在此，__init__我们创建QPlainTextEdit将包含日志的 。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到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

Create an object from this class, passing it the parent for the QPlainTextEdit(e.g. the main window, or a layout). You can then add this handler for the current logger.

从这个类创建一个对象，将它的父对象传递给QPlainTextEdit（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)

回答by Todd Vanyo

Here's a complete working example based on mfitzp's answer:

这是一个基于mfitzp 回答的完整工作示例：

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_()

回答by Alex

Adapted from Todd Vanyo's example for PyQt5:

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_())

回答by Chweng Mega

Alex's answer should be ok in a single thread scenario, but if you are logging in another thread (QThread) you may get the following warning:

Alex 的回答在单线程场景中应该没问题，但是如果您登录另一个线程（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().)

This is because you are modifying the GUI (self.widget.appendPlainText(msg)) from a thread other than the main thread without using the Qt Signal/Slot mechanism.

这是因为您正在self.widget.appendPlainText(msg)从主线程以外的线程修改 GUI ( ) 而不使用 Qt 信号/插槽机制。

Here is my solution:

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
   ...

回答by tobilocker

Thread-safe version

线程安全版本

class QTextEditLogger(logging.Handler, QtCore.QObject):
    appendPlainText = QtCore.pyqtSignal(str)

def __init__(self, parent):
    super().__init__()
    QtCore.QObject.__init__(self)
    self.widget = QtWidgets.QPlainTextEdit(parent)
    self.widget.setReadOnly(True)
    self.appendPlainText.connect(self.widget.appendPlainText)

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

Usage

用法

    logTextBox = QTextEditLogger(self)

    # log to text box
    logTextBox.setFormatter(
        logging.Formatter(
            '%(asctime)s %(levelname)s %(module)s %(funcName)s %(message)s'))
    logging.getLogger().addHandler(logTextBox)
    logging.getLogger().setLevel(logging.DEBUG)

    # log to file
    fh = logging.FileHandler('my-log.log')
    fh.setLevel(logging.DEBUG)
    fh.setFormatter(
        logging.Formatter(
            '%(asctime)s %(levelname)s %(module)s %(funcName)s %(message)s'))
    logging.getLogger().addHandler(fh)