Sep-01-2020, 02:56 PM
I don't understand why, but it is a common misconception by many new programmers on this forum that everything needs a variable, as in if you have 4 things you must need 4 variables. I don't know where this thinking comes from, but it is common enough that there must be some popular resource perpetuating this fallacy.
Variables are bad. Necessary, but bad. Every variable is extra code and extra potential for making mistakes. Your programs should only use as many variables as are necessary and no more. In your example you should only have 1 variable, the list of VIN numbers. Unless there is something really special about the second VIN number why should it have a variable? That can be a kind of test for deciding to use a variable. If something is "special" it probably deserves a variable, else treat it as part of a collection or ignore it.
What do I mean by "treat it as part of a collection"? In this example you have a list of VIN numbers. In the "real world" each VIN number represents something unique and special, but a program is not the real world and a VIN number is just a unique ID. Nothing special about that. Your program needs to remember VIN numbers, so there has to be some way to save them and access them and probably process them, but this will be the same for all the VIN numbers. When you have a bunch of related things like this it is best to treat them as faceless entities in a collection.
What do I mean by "ignore it"? I see a lot of Python code on this forum that makes variables for things that should be thrown away. This is particularly true in the GUI discussion group. Almost everything returned by a tkinter call should be thrown away. After I place my controls I don't need to remember the frame that holds them. Depending how I write my code I don't have to remember the handles for my controls and displays. This stuff is important when you are making things, but once you move into running things they are no longer referenced. If you are done using something, throw it away. Python is good at recycling
Variables are bad. Necessary, but bad. Every variable is extra code and extra potential for making mistakes. Your programs should only use as many variables as are necessary and no more. In your example you should only have 1 variable, the list of VIN numbers. Unless there is something really special about the second VIN number why should it have a variable? That can be a kind of test for deciding to use a variable. If something is "special" it probably deserves a variable, else treat it as part of a collection or ignore it.
What do I mean by "treat it as part of a collection"? In this example you have a list of VIN numbers. In the "real world" each VIN number represents something unique and special, but a program is not the real world and a VIN number is just a unique ID. Nothing special about that. Your program needs to remember VIN numbers, so there has to be some way to save them and access them and probably process them, but this will be the same for all the VIN numbers. When you have a bunch of related things like this it is best to treat them as faceless entities in a collection.
What do I mean by "ignore it"? I see a lot of Python code on this forum that makes variables for things that should be thrown away. This is particularly true in the GUI discussion group. Almost everything returned by a tkinter call should be thrown away. After I place my controls I don't need to remember the frame that holds them. Depending how I write my code I don't have to remember the handles for my controls and displays. This stuff is important when you are making things, but once you move into running things they are no longer referenced. If you are done using something, throw it away. Python is good at recycling