Logging events in Python; How to log events inside classes?

Question

Hello guys.

I built (just for fun) 3 classes to help me log some events in my work.

here are them:

class logMessage:

    def __init__(self,objectName,message,messageType):
        self.objectName = objectName
        self.message = message
        self.messageType = messageType
        self.dateTime = datetime.datetime.now()

    def __str__(self):
        return str(self.dateTime) + "\nObjeto de valor " + str(self.objectName) + " gerou uma mensagem do tipo: " + self.messageType + "\n" + self.message + "\n"

class logHandler():

    def __init__(self):
        self.messages = []

    def __getitem__(self,index):
        return self.messages[index]

    def __len__(self):
        return len(self.messages)

    def __str__(self):
        colecaoString = ""
        for x in self.messages:
            colecaoString += str(x) + "\n"

        return colecaoString

    def dumpItem(self,index):
        temp = self.messages[index]
        del self.messages[index]
        return str(temp)

    def append(self,log):
        if isinstance(log,logMessage.logMessage):
            self.messages.append(log)
        else:
            self.newLogMessage(log, "Wrong object type. Not a log message. Impossible to log.","Error")

    def newLogMessage(self,objectInstance,message,messageType):
        newMessage = logMessage.logMessage(objectInstance,message,messageType)
        self.append(newMessage)

Here is my question:

Imagine i have other classes, such as Employee, and i want to log an event that happened INSIDE that class.

How can i do that without always passing a logHandler instance to every other class i want to log? My idea would be to pass a logHandler to every init function, and then use it inside it.

How can that be done, without doing what i specified?

How would it work with global logHandler? Is there a way to discover in runtime if there is a logHandler instance in the program, and use it to create the messages?

Thanks

Answer 1

Just create an instance of your classes in the module you posted. Then just import your logging module in every file you want to log from and do something like this:

yourloggingmodule.handler.newLogMessage(...)

Where handler is the name of the instance you created.

Answer 2

You could use the Borg pattern, meaning you can create local instances of your logger object and yet have them access the same state. Some would say that is elegant, others may say it's confusing. You decide. :)