CODEWITHSUNDEEP
pythonuser-interfacewxpython
user1401950
user1401950

Reputation: 995

How to use `wx.ProgressDialog` with my own method?

How can I use the wx.ProgressDialog to time my method called imgSearch? The imgSearch method finds image files on the user's pc. How can I make the wx.ProgressDialog run while imgSearch is still running and display how long the imgSearch is taking?

Here's my code:

def onFind (self,event)# triggered by a button click
    max = 80
    dlg = wx.ProgressDialog("Progress dialog example","An informative message",parent=self, style = wx.PD_CAN_ABORT| wx.PD_APP_MODAL| wx.PD_ELAPSED_TIME| wx.PD_REMAINING_TIME)

    keepGoing = True
    count = 0
    imageExtentions = ['*.jpg', '*.jpeg', '*.png', '*.tif', '*.tiff']
    selectedDir = 'C:\\'
    imgSearch.findImages(imageExtentions, selectedDir)# my method

    while keepGoing and count < max:

    count += 1
    wx.MilliSleep(250)

    if count >= max / 2:
        (keepGoing, skip) = dlg.Update(count, "Half-time!")
    else:
        (keepGoing, skip) = dlg.Update(count)

    dlg.Destroy()

Upvotes: 2

Views: 3047

Answers (1)

acattle
acattle

Reputation: 3113

The Problem

Your question is vague but after looking at your code I am going to guess that your problem is that imgSearch.findImages() completes before the dialog ever even opens. I'd appreciate if you could edit your question so I know if this is correct.

I see you are using code from this tutorial to show you how to use wx.ProgressDialog. Unfortunately, you are taking a rather naive approach to this. The purpose of that tutorial is to introduce readers to a wide range of built-in dialogs. As such, the wx.ProgressDialog example is a simple example simply to show you the methods, not to be used as an implementation.

Background Information

First, you need to know what multithreading is and how it works. Everything a computer does is broken down into a series of mathematical operations. The computer processor can only do one operation at a time. Therefore, the computer can only do one thing at a time. Now you might be thinking "well that isn't true. I'm listening to an MP3 while browsing the internet. That's at least two things". Well you're right and you're wrong. Imagine a chef. A chef can prepare many dishes at once but he can only pay attention to them one at a time. Therefore, he must switch between the dishes, performing some small task, until they are all complete. That's how a computer multitasks. Instead of "dishes", computers switch between "threads".

The Solution

Step 1: Threading

By default wxPython is only a single thread (this isn't exactly true, but just go with it). wxPython literally runs your code line-by-line such that one line must finish completely before the next line is run. Therefore, while imgSearch.findImages() is running no other code is executing and it must complete before the wx.ProgressDialog can even be created. The good news is that there are several ways to fix this. The bad news is that fixing this can become quite complicated. I'm not an expert but I suggest doing a search for "wxpython threading" and trying to find some tutorials. I found this tutorial but it is fairly old. The main point is that you will need to run imgSearch.findImages() in it's own thread so that it does not block the GUI.

Step 2: Metrics

So now, how do you make the wx.ProgressDialog reflect the actual status of imgSearch.findImages()? Well, that depends. You need to find some metric to help you measure how much has been done and how much more is left to do. In your code the metric is time because the progress is programmed to take 80 * 250ms = 20s. Time probably isn't what you want. You will need to decide what is best for your program but I will use the example of "number of folders" because it's easy to understand. I will count the total number of folders as well as the number of folders I have completely scanned. Now there's two ways to initialize your metric. You can calculate the max you need if the number is small or easy to calculate (such as time) or you can take a dynamic approach. In my case, calculating "number of folders" exactly would require almost as much time as the image search itself so dynamic is the best option. So, I would modify imgSearch.findImages() so that it keeps a count of the number of folders it has seen as well as the number of folders it has scanned (e.g. if my starting location has 3 folders I start with 3/0. I begin scanning the first folder which itself contains 2 more folders, so I now have 5/0. Every time I completely scan a folder I add 1 to the number of scanned folders, i.e. 5/1 after scanning one folder.). Knowing how many folders I have scanned and how many folders I have left to scan I can estimate my percentage completion using # of folders scanned / total # of folders. 1 / 5 = 0.20, therefore I estimate that I am 20% complete (note that if the next folder I scan contains 5 more folders then this number is automatically decreased to 10%. That is why I called 20% an estimate)

Step 3: Updating

So by now we should have imgSearch.findImages() in it's own thread and it should be able to estimate how far from completion it is. Now we need to update the wx.ProgresDialog. My favourite method for these types of problems is using the pubsub library. Basically, the imgSearch.findImages() thread must occasionally send a message which says how close to completion it is. Maybe at the end of each folder. Maybe ever three folders. It's up to you. Next, you will need to create a method in your main GUI's thread which can read these messages and update wx.ProgressDialog accordingly.

It's a lot of work but I wish you the best of luck.

Upvotes: 5

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