Python - different variable with each function run

问题

I'll try explain this as well as I can. I've created a function that uses Tkinter's tkFileDialog.askopenfilename() to let you select a photograph. The script comes back with the coordinates in two variables:

def getCoordinates():

    # code to get coordinates here

    # variables for lat and long
    global latitude
    global longitude

    latitude
    longitude

Now, I've created a function that calls the first function getCoordinates() TWICE. So this asks for TWO photographs to be selected.

def TwoPic():
    run = 0
    while run < 2:
        run = run + 1
        getCoordinates()

        FirstRunLat = latitude
        FirstRunLong = longitude
        print FirstRunLat + " " + FirstRunLong

        SecRunLat = latitude
        SecRunLong = longitude
        print SecRunLat + " " + SecRunLong

        ThirdRunLat = latitude
        ThirdRunLong = longitude
        print ThirdRunLat + " " + ThirdRunLong

    root.quit()

What basically will happen, is that the SecRunLat & SecRunLong and the ThirdRunLat & ThirdRunLong will end up being the same as FirstRunLat and FirstRunLong.

So what I'm asking is, how can I run the function to get coordinates and give the variables different names that stay unique and don't get duplicated if I run the function again?

Hope this makes sense.

Thank you very much in advance.

回答1:

Well, if you want to keep on using globals, I would just use lists:

def TwoPic():
    run = 0
    Lats = []
    Longs = []
    while run < 2:
        run = run + 1
        getCoordinates()

        Lats.append(latitude)
        Longs.append(longitude)

    root.quit()

回答2:

You return values from your function, and assign them as a tuple:

def getCoordinates():
    # code to get coordinates here

    return latitude, longitude

and when calling these:

def TwoPic():
    run = 0
    while run < 2:
        run = run + 1

        FirstRunLat, FirstRunLong = getCoordinates()

        print FirstRunLat + " " + FirstRunLong

        SecRunLat, SecRunLong = getCoordinates()
        print SecRunLat + " " + SecRunLong

        ThirdRunLat, ThirdRunLong = getCoordinates()
        print ThirdRunLat + " " + ThirdRunLong

    root.quit()

Don't use globals to pass around function results; that's what the return statement is for.

回答3:

What basically will happen, is that the SecRunLat & SecRunLong and the ThirdRunLat & ThirdRunLong will end up being the same as FirstRunLat and FirstRunLong.

Of course - you don't change the value in-between, as you call getCoordinates() only once.

It would be much better to return your results:

def getCoordinates():

    # code to get coordinates here

    return latitude, longitude # as a tuple.

def TwoPic():
    run = 0
    results = []
    while run < 2:
        run = run + 1

        lat, lng = getCoordinates()
        print lat + " " + lng
        results.append((lat, lng))
    print results

    root.quit()

来源：https://stackoverflow.com/questions/21403178/python-different-variable-with-each-function-run

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