didn't know about the = option, but once I saw it once, I guessed right a few times
never used ^ in Python, and didn't make the connection to XOR (I figured I'd need the math library or something)
the r and a with =! (again, never used = option)
edge cases in walrus operator and other things unrelated to f-strings
Most of those I missed (and many I got) I'd reject a PR over because it's not obvious enough what's going on. But I think given that, I did reasonably well.
if (x := some_function()):
do_something(x)
else:
# x is None or False or something, consider it invalid
The only thing I wish was different is adding a scope, which would make x invalid outside the block. But Python's scoping rules are too dumb to handle this case.
I think my most common use case is with dictionary lookups.
if (val := dct.get(key)) is not None:
# do something with val
I've also found some cases where the walrus is useful in something like a list comprehension. I suppose expanding on the above example, you you make one that looks up several keys in a dict and gives you their corresponding values where available.
vals = [val for key in (key1, key2, key3) if (val := dct.get(key)) is not None]
In lots of functional languages, you'd have some_function() return an Option type and then you'd use .map() or similar on it to only do something when the value is defined. I think, that can be done in Python's syntax, but you need a library for the Option type...
Python has an "Optional" type, but it's merely an alias for T | None. I wish Python had better support for FP, but each time it gets close, it doesn't quite go far enough.
For example, it now has match blocks, but there's no error if the match is exhaustive, which hurts formal proofs of correctness. Likewise, tons of other features fall a bit short, but in general it's workable with some discipline.
Walrus operator does an inline assignment to a variable and resolves to the value assigned. If it is in a condition statement, like "if x := y:", it assigns the value of y to x then interprets the expression of the condition as of it just said "if x:". Functionally, that means the assignment happens regardless of the value of y, but the condition only passes if the value of y is "truthy", i.e. if it's not None, an empty collection, numerically equal to zero, or just False.
To be fair this was quite wtf-free. Mostly just unimportant formatting subtleties and stuff you'd never write.
Python definitely has bigger WTFs, like bool being an int, implicit bool conversion, implicit iteration of strings, etc.
Bool being an int was part of this.
Sure but that's orthogonal to f-strings.
Hmm: 17/26
Failures were:
=option, but once I saw it once, I guessed right a few times^in Python, and didn't make the connection to XOR (I figured I'd need the math library or something)Most of those I missed (and many I got) I'd reject a PR over because it's not obvious enough what's going on. But I think given that, I did reasonably well.
But I learned something. Thanks for the post!
This is fun, as was the JS date one. I hope people do more.
Still though, I don't think doing well or not on these necessarily mean you're good or bad with the language.
Walrus operator. What did I just read?
I love the walrus operator:
The only thing I wish was different is adding a scope, which would make
xinvalid outside the block. But Python's scoping rules are too dumb to handle this case.Walrus is more useful in a while loop.
I think my most common use case is with dictionary lookups.
I've also found some cases where the walrus is useful in something like a list comprehension. I suppose expanding on the above example, you you make one that looks up several keys in a dict and gives you their corresponding values where available.
In lots of functional languages, you'd have
some_function()return anOptiontype and then you'd use.map()or similar on it to only do something when the value is defined. I think, that can be done in Python's syntax, but you need a library for theOptiontype...Python has an "Optional" type, but it's merely an alias for
T | None. I wish Python had better support for FP, but each time it gets close, it doesn't quite go far enough.For example, it now has
matchblocks, but there's no error if the match is exhaustive, which hurts formal proofs of correctness. Likewise, tons of other features fall a bit short, but in general it's workable with some discipline.Walrus operator does an inline assignment to a variable and resolves to the value assigned. If it is in a condition statement, like "if x := y:", it assigns the value of y to x then interprets the expression of the condition as of it just said "if x:". Functionally, that means the assignment happens regardless of the value of y, but the condition only passes if the value of y is "truthy", i.e. if it's not None, an empty collection, numerically equal to zero, or just False.
::: spoiler Tap for spoilers I was sure something was wrong with the first question, probably because of the linter in my editor.
TIL about the feature in #4, it'll be handy in my day-to-day businesses.
I forgot about the escaping in #7.
#19: what?
From then on, it was all [uneducated] guesses. :::
12/26, need more practice.