设置用户友好和显式标志值的最 Pythonic 方式？

Question

What's the most Pythonic way of giving flags values that are user-friendly and self-evident for whoever is reading the code?

Assume I got the following method for a class, which depending on the input will calculate a certain multiplier and set a cracking_mode flag for that class instance:

def evaluate_first_matrix_crack(self, base_sigma22, base_tau12):
    # Mixed transverse tension-shear
    if base_sigma22 > 0 and base_tau12 != 0:
       self.cracking_mode = 2
       multiplier = sqrt(1. / ((base_sigma22 / self.Yt_is) ** 2 + (base_tau12 / self.S_is) ** 2))

    # Pure transverse tension
    elif base_sigma22 > 0 and base_tau12 == 0:
        self.cracking_mode = 0
        multiplier = self.Yt_is / base_sigma22

    # Pure shear
    elif base_sigma22 <= 0 and base_tau12 != 0:
       self.cracking_mode = 1
        multiplier = self.Yt_is / base_sigma22

    return multiplier

The "cracking_mode" flag will affect which methods are called in other sections of the code. I want the flag values to be as user-friendly as possible, so that when they are checked through if statements in other sections of the code, the reader can immediately tell which flag value corresponds to which option.

So rather than having self.cracking_mode = 2 I would ideally have self.cracking_mode = "mixed_transverse_tension_shear" .

However, I don't think that's a Pythonic way of doing things, aside from the fact that comparing strings takes longer than comparing integers.

So what would be the most Pythonic (and user-friendly) way of solving the issue?

Answer 1

This is exactly the purpose of enum in other languages. In my opinion, the most "pythonic" way to do things is simply the clearest - so string comparison isn't that bad. Probably a little better would be to create constants that represent the values ( MIXED_TRANVERSE_TENSION_SHEAR = 2 ) as static class members, and then compare to those constants, which is a more efficent integer comparison.