this post was submitted on 26 Jul 2025
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Python

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Python f-string quiz (fstrings.wtf)
submitted 2 weeks ago by learnbyexample@programming.dev to c/python@programming.dev
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[–] Eheran@lemmy.world 8 points 2 weeks ago (2 children)

Walrus operator. What did I just read?

[–] sugar_in_your_tea@sh.itjust.works 12 points 1 week ago (2 children)

I love the walrus operator:

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.

[–] joyjoy@lemmy.zip 6 points 1 week ago

Walrus is more useful in a while loop.

while (data := f.read(1024)):
    pass
[–] tunetardis@piefed.ca 2 points 1 week ago

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]
[–] kryptonianCodeMonkey@lemmy.world 2 points 1 week ago* (last edited 1 week ago)

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.