How can an int be '+' with a tuple?

[Jach Fong]

The attached is a script which can run under Python 3.4/Windows Vista
correctly. One thing make me puzzled is that the "any + context" at line
18. The "any" was passed as an integer from line 43 and the "context"
was defined as a tuple at line 35. This concatenation works! how?

Best Regards,
Jach Fong





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import _thread as thread
import queue
threadQueue = queue.Queue(maxsize=0)

def queueChecker(widget, delayMsecs=100):
    try:                                                
        (callback, args) = threadQueue.get(block=False)
    except queue.Empty:
        pass
    else:
        callback(*args)

    widget.after(delayMsecs,
        lambda: queueChecker(widget, delayMsecs)) # back to event loop

def threaded(action, args, context, onExit, onProgress):
    def progress(*any):
        threadQueue.put((onProgress, any + context))
    action(progress=progress, *args)
    threadQueue.put((onExit, context))

def startThread(action, args, context, onExit, onProgress):
    thread.start_new_thread(
        threaded, (action, args, context, onExit, onProgress))

if __name__ == '__main__':
    import time
    import tkinter as tk

    def onEvent(i):  # code that spawns thread
        myname = 'thread-%s' % i
        startThread(
            action     = threadaction,
            args       = (i, 3),
            context    = (myname,),
            onExit     = threadexit,
            onProgress = threadprogress)

    # thread's main action
    def threadaction(id, reps, progress):
        for i in range(reps):
            time.sleep(1)
            progress(i)  # progress callback: queued

    # thread exit/progress callbacks: dispatched off queue in main thread
    def threadexit(myname):
        print('%s\texit' % myname)

    def threadfail(exc_info, myname):
        print('%s\tfail\t%s' % (myname, exc_info[0]))
        
    def threadprogress(count, myname):
        print('%s\tprog\t%s' % (myname, count))

    # make enclosing GUI and start timer loop in main thread
    # spawn batch of worker threads on each mouse click: may overlap
    root = tk.Tk()
    queueChecker(root)
    root.bind('<Button-1>',   # 3.x need list for map, range ok
              lambda event: list(map(onEvent, range(2))) )
    root.mainloop()