[Tutor] Problems with Gauge Bar.

Alan Gauld alan.gauld at btinternet.com
Sun Aug 10 19:23:22 CEST 2008

"Olrik Lenstra" <o.lenstra at gmail.com> wrote

> I'm probably asking for a lot here. But I don't think I understand 
> this
> fully.

Thats OK.

>> def onScan(self):
>>    self.myfile = open('foo.txt')
>>    self.count = 0
>>    self.setTimer(0.01, self.processLine)
>> def processLine(self)
>>   line = self.myfile.readline()
>>   if line:
>>       processLine(line)
>>       self.count += 1
>>       self.myGauge.setValue(count)
>>       self.setTimer(0.01, self.processLine)
>>   else:
>>      self.myGuage.setValue(0)

> Ok. So lets see if I got this right. In the onScan you define 
> self.myfile to
> open 'foo.txt' One thing I don't get here is what is foo.txt used 
> for?

Its the file that you want to scan - assuming there is a file.
It could be a list or anything else - I don't actually know from
your code what onScan is supposed to do! :-)

> Then you set the count to 0
> Then you set the timer to 0.01 with the event processLine?

Thats right. The idea is to set up a timer to fire after 1/100 of a 
Then in processLine set up another one after processing each line
until the file (or list etc) is scanned.

> then in the processLine you add 1 to the count with every line that 
> is read?

Yes and set the Guage value to whatever count is. Then next time
the GUI draws itself the new cvalue will appear in the guage.

The important bit is that:
1) We use onScan to initialise things not to actually do the 
2) We create the timer each time we process some data (you could
    opt to process more than one line - say batches of 10, but the
    important point is that its only ever a short period of 
3) We update the count and then the guage after each batch completes


Alan Gauld
Author of the Learn to Program web site

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