python declaration of constant beginning with number

Question

I have a python module with definitions of constants. They look like so:

30KHZ = 0b000
125KHZ = 0b001
250KHZ = 0b010
1MHZ = 0b011

Obviously, these are not allowed names. One way of to deal with this is to prepend names with something. Names like _30KHZ look nice, but they mess with static analyzers. Names like S_30KHZ or F30KHZ are allowed, but they look awkward and the meaning of the S_ or F may be unclear. Another way is to rotate the name like so: KHZ30. But is doesn't look good either.

How to name such constants to make their meaning obvious to the user?

Since these appear to be frequencies, I would opt for the longer name freq_30khz and so on. explicit is better than implicit. — modesitt
– modesitt, Commented Aug 20, 2018 at 15:11
Better yet, are the exact frequencies important, or does the user just need to know that these are, for instance, low, medium, high, and very high frequencies? — chepner
– chepner, Commented Aug 20, 2018 at 15:13
I would say FREQ_30HZ, using capital letters and underscores only for constants. — Laurent H.
– Laurent H., Commented Aug 20, 2018 at 15:14

Bryan Oakley · Accepted Answer · 2018-08-20 15:24:57Z

2

I would probably put these in a dictionary:

BITMAPS = {
    "30KHZ": 0b000,
    "125KHZ": 0b001,
    "250KHZ": 0b010,
    "1MHZ": 0b011,
}

answered Aug 20, 2018 at 15:24

Bryan Oakley

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3 Comments

FHTMitchell Over a year ago

arguably even better bitmaps = {30: 0b000, 125: 0b001, 250: 0b010, 1000: 0b011} then you can just access using their value.

Sergey Over a year ago

For some reason when I think about constants in python, I think "dot notation"

Bryan Oakley Over a year ago

@Sergey: sure. In this case, however, you can't use dot notation since the keys are numbers (or being with numbers), so you have to do something different.

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