this post was submitted on 08 Dec 2023
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Programmer Humor

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know the features of your language (lemmy.world)
submitted 2 years ago by jroid8@lemmy.world to c/programmerhumor@lemmy.ml
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[–] stebo02@sopuli.xyz 21 points 2 years ago (3 children)

Python:

return a or b

i like it because it reads like a sentence so it somewhat makes sense

and you can make it more comprehensive if you want to:

return a if a is not None else b

[–] Turun@feddit.de 14 points 2 years ago* (last edited 2 years ago)

This diverges from the OP code snippets if a has the value False.

[–] alehc@lemmy.world 7 points 2 years ago (1 children)

I personally dislike this because when you read "or" you expect some boolean result not a random object :/

[–] stebo02@sopuli.xyz 3 points 2 years ago

there's always the second option for you

[–] rwhitisissle@lemmy.ml 0 points 2 years ago (1 children)

For newer python people, they see return a or b and typically think it returns a boolean if either is True. Nope. Returns a if a is truthy and then checks if b is truthy. If neither are truthy, it returns b.

[–] cypherpunks@lemmy.ml 6 points 2 years ago* (last edited 2 years ago) (1 children)

Returns a if a is truthy and then checks if b is truthy. If neither are truthy, it returns b.

Not quite. If a is not truthy, then the expression a or b will always return b.

So, there is never any reason to check the truthiness of b.

you can paste this in your repl to confirm it does not.

class C:
 def __repr__(self): return [k for k, v in globals().items() if v is self][0]
 def __bool__(self):
  print(f"{self}.__bool__() was called")
  return False

a, b = C(), C()
print(f"result: {a or b}")

spoiler output

a.__bool__() was called
result: b

:::

[–] rwhitisissle@lemmy.ml 3 points 2 years ago

Ah, good catch.