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| | The right answer is all the time, but in practice people go to more effort when they expect the program to be around for a longer time. Also in practice programs tend to be around longer than you expect. Try to develop good habits, it will pay off. | | The right answer is all the time, but in practice people go to more effort when they expect the program to be around for a longer time. Also in practice programs tend to be around longer than you expect. Try to develop good habits, it will pay off. |
| | = Short vs Long = | | = Short vs Long = |
| − | Really short names are rarely good they just have too little meaning. You should remember that a program is more often read than written ( only once not counting fix up ) so make it easy to read. That said names can get too long. Over 12 characters?: take a second look. Abbreviation are fine but should be consistent. I use hi and lo for high and low, max and min for maximum and minimum. But n for number? Too short, also may hide an important function n(). | + | Really short names are rarely good they just have too little meaning. You should remember that a program is more often read than written ( only once not counting fix up ) so make it easy to read. That said names can get too long. Over 12 characters?: take a second look. Abriviations are fine but should be consistent. I use hi and lo for high and low, max and min for maximinum and minimum. But n for number? Too short, also may hide an important function n(). |
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| − | Short vs long also applies to how long the variable will exist, or be in scope. If the scope of a variable is short, it is easier to live with a short, and less clear, name. I use ix for a index with short scope, if the scope is longer then I might use ix_toy if the index is indexing into a list of toys. | + | Short vs long also applies to how long the variable will exist, or be in scope. If the scope of a variable is short, it is easier to live with a short, and less clear, name. |
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| − | = Singular vs Plural =
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| − | Often I use a plural for a list, a list of toys might be toys, an element in it a toy ( or a_toy, or if indexing through the list ix_toy for the numerical index and i_toy for toys[ix_toy].
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| − | <pre>
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| − | for ix_toy, i_toy enumerate( toys ):
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| − | i_toy.my_index = ix_toy # not necessarily a useful example of code
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| − | </pre>
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| − | = Generic Variables =
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| − | Sometimes it is useful to use generic names rather than specific ones. One use I often encounter is in constructing tkiner gui's. Say I want a button, and want to configure it in some specific way:
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| − | <pre>
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| − | a_button = Button( a_frame , width=10, height=2, text = "Edit Parms" )
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| − | a_button.config( command = self.controller.os_open_parmfile )
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| − | a_button.pack( side = LEFT )
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| − | </pre>
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| − | This is fine, but I often copy the code and use it for a different widiget ( many widgets use the same sorts of parameters and setup functions. Then I may ue a more generic name.
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| − | <pre>
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| − | # record checkbox
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| − | cb_record_var = IntVar()
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| − | a_widget = Checkbutton( a_frame, text="Record", variable=cb_record_var, width = 10, anchor="w" )
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| − | a_widget.config( command = lambda ix = ix__smartplug_adapter: self.controller.cb_device_action( ix, "record" ) )
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| − | a_widget.config( borderwidth = 5, relief = RAISED, )
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| − | a_widget.grid( row = lrow * rowspan, column = lcol, rowspan = 2, sticky=E + W + N + S )
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| − | i_smartplug_adapter.gui_tk_record_checkbox_var = cb_record_var
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| − | lcol += 1
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| − | # time combobox
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| − | times = ( "infinite", .1, .5, 1, 2, 3, 5, 10, 15, 20, 25, 30, 40, 50, 60 )
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| − | a_widget = ttk.Combobox( a_frame, values=times, state='readonly', width = 10, )
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| − | a_widget.current( 6 ) # set default value
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| − | a_widget.grid( row = lrow * rowspan, column = lcol, rowspan = rowspan, sticky=E + W + N + S )
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| − | i_smartplug_adapter.gui_tk_combo = a_widget
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| − | lcol += 1
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| − | </pre>
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| − | = Local Variables =
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| − | Local variables are fast, and may be useful as generic variables ( see above ). But some times as for the combo box ( above ) you need a reference to be used later ( i_smartplug_adapter.gui_tk_combo = a_widget ). But it is useful and ( I think faster and easier ) to use a more generic local variable for the set up and initial manipulations, and save the reference at the end ).
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| | = Avoid Reserved Words = | | = Avoid Reserved Words = |
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| | def display_help(): # verb like | | def display_help(): # verb like |
| | </pre> | | </pre> |
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| − | = Declare at top of Class =
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| − | Actually Python does not have declarations but for me this means do an assignment in __init__ or very nearby and comment the variables. Sometimes this is a natural part of the initialization, other times it is not, perhaps because the value is not know yet. In this case assign it to None.
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| − | <pre>
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| − | self.live_graph_lines = None # lines on the graph, we keep for later updating
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| − | </pre>
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| − | = Variables =
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| − | Most programming languages have variables, and Python users often refer to variables, but actually, sort of, '''Python does not have variables''' it has '''names'''. Is this a difference that makes a difference? If I say:
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| − | <pre>
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| − | self.monitor_state = 1
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| − | # then....
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| − | self.monitor_state = 2
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| − | </pre>
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| − | Then self.monitor_state has changed or varied, so it must be a variable. Yes and No. self.monitor_state is a name and at one time it "pointed to" a value of 1 and later it "pointed to" a value of 2. A mutable object is in some ways more like a variable. I will not say more here, but at some point you might want to investigate this issues because, sometimes, they make a difference.
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| − | You may find this useful: '''[https://www.youtube.com/watch?v=4MCT4WLf7Ac&__s=dibfsizig3wuxjywoekt (26) "Python Oddities Explained" - Trey Hunner (PyCon AU 2019) - YouTube ]''' and '''[https://treyhunner.com/python-oddities/#/3 Python Oddities Explained ]'''
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| | = Class Instance Variables = | | = Class Instance Variables = |
