Omitting repetition in long statements

Question

I have a quite long statement:

if LongClassName.results[variable1][longerVariable2][variable3] == 0:
   LongClassName.results[variable1][longerVariable2][variable3] = 42

As one can clearly see, there is quite a lot of repetition in this code (the same expression is used in the conditional and in its body). Is there a way of simplifying it? In C++ I could use references, like this:

auto &ref = LongClassName.results[variable1][longerVariable2][variable3];
if (ref == 0) {
    ref = 42;
}

What is the Pythonic way of simplifying this expression?

declaring, referencing, and setting a variable is (mostly) language agnostic > https://www.pythonforbeginners.com/basics/python-variables — RandomUs1r, Oct 19 '18 at 21:00
@Robin (and @RandomUs1r): Python doesn't have references, so the `ref = 42` wouldn't work with what you're suggesting. — martineau, Oct 19 '18 at 21:00
As stated [in this answer](https://stackoverflow.com/a/3106752/10484131) it's the Pythonic way to be explicit. — Felix, Oct 19 '18 at 21:00
@martineau - sorry, yeah, you're right. I hadn't noticed that an actual assignment was going on. — Robin Zigmond, Oct 19 '18 at 21:03

score 2 · Accepted Answer · edited Oct 19 '18 at 21:12

2

You can stop and grab the reference a level above this:

partial_ref = LongClassName.results[variable1][longerVariable2]
if partial_ref[variable3] == 0:
   partial_ref[variable3] = 42

That's not particularly Pythonic, but it's the closest to your original C++ code.

edited Oct 19 '18 at 21:12

user2357112

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answered Oct 19 '18 at 21:06

Prune

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score 2 · Answer 2 · answered Oct 19 '18 at 21:07

You could shorten it to some degree like this:

container = LongClassName.results[variable1][longerVariable2]
if container[variable3] == 0:
   container[variable3] = 42

Python doesn't have totally general references like C++ does, so this creates a shorter name for the container of variable3 and uses its name in subsequent statements.

anon · Answer 3 · 2018-10-19T21:04:56.330

-1

x = LongClassName.results[variable1][longerVariable2]
if x[variable3] == 0:
   x[variable3] = 42

that works but doesn't seem very elegant.

edited Oct 19 '18 at 21:04

answered Oct 19 '18 at 20:59

anon

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2

@jasonharper: Poster changed they're answer since you posted your comment—so it's now like the others and will actually work. – martineau Oct 19 '18 at 21:12

Omitting repetition in long statements

3 Answers3