3 ms·

Despite the URL, I’d only consider a few of these to be WTFs. Questions 20 & 21 definitely are, though: >>> a = 42 >>> print(f"{a:=10}") 42 >>>

by pansa2 1y ago

Despite the URL, I’d only consider a few of these to be WTFs. Questions 20 & 21 definitely are, though: >>> a = 42 >>> print(f"{a:=10}") 42 >>> print(f"{(a:=10)}") 10 I still can’t believe anyone thought the walrus operator was a good idea.

almostgotcaught 1y ago
this has nothing to do with the walrus operator and everything to do with how string.format works in python https://docs.python.org/3/library/string.html#format-string-syntax https://docs.python.org/3/library/string.html#format-string-... Edit: someone downvoted me because they don't understand there is no walrus operator here print(f"{a:=10}")
- lyu07282 1y ago
  They obviously meant the second example: >>> print(f"{(a:=10)}")
  - almostgotcaught 1y ago
    the output of the second example is "obvious" so i don't see the problem.
    - pansa2 1y ago
      Neither of the examples is problematic on its own; it's the fact that the language supports both of them. They're very hard to distinguish at-a-glance yet behave entirely differently.
sfink 1y ago
You can pry the walrus operator from my cold dead hands. m = re.match(pattern1, line) if m: do_stuff(m.group(1)) else: m = re.match(pattern2, line) if m: do_other_stuff(m.group(2)) else: m = re.match(pattern3, line) if m: do_things(m.groups()) else: m = ... Obviously, there are ways to improve this particular example without using the walrus. But it's also usually not this simple. I run into something like this all the time. Not many times per program, and I don't actually use the walrus all that often, but when it's the right thing it's so very nice.
- marcosdumay 1y ago
  You know, creating functions is allowed in Python. As are loops. The assignment is the least problematic thing on that code. I do even disagree on it being a problem.
- callc 1y ago
  Even though I’ve never used python walrus, I’m a huge fan of the “X language feature can be used as an expression” I feel the same way with rust control flow being used as an expression, and am disappointed when other languages don’t have it. Even though one could argue it makes things more complicated, I feel more mental freedom and feel the language getting out of the way.
- pansa2 1y ago
  The walrus operator hardly changes that example at all: if m := re.match(pattern1, line): do_stuff(m.group(1)) else: if m := re.match(pattern2, line): do_other_stuff(m.group(2)) else: if m := re.match(pattern3, line): do_things(m.groups()) else: m = ... I've found `:=` useful in the headers of `while` loops, but that's about it. The complexity that walrus adds to the language far outweighs its usefulness.
  - ghewgill 1y ago
    The walrus operator allows you to use `elif` there to avoid cascading indentation. if m := re.match(pattern1, line): do_stuff(m.group(1)) elif m := re.match(pattern2, line): do_other_stuff(m.group(2)) elif m := re.match(pattern3, line): do_things(m.groups()) else: ...
    - pansa2 1y ago
      Ah, I missed that. Thanks
    - sfink 1y ago
      ...and for me, the benefit is that this is much more clear to me when reading the code. An increasing level of indentation directly maps to needing to keep more in my head. (Sure, in this case you can pattern match and see that there's nothing else, but in general you need to watch out for cases where the else may be doing more than just the next check on the same inputs. ) But the walrus is good even in the absence of a series of matches. It is quite common to need to know more than the boolean "did this match or not?", and so to my eye it is much cleaner to have one line doing the test and the next lines using the results. I don't care about saving characters or even lines. `m = ...match...` immediately followed by `if m:` feels like overhead for the sake of the programming language's limitations; it's extraneous to what I want to express. Also, I assert that the pattern is better for correctness. It's like Rust's `if let Some(foo) = f() { ... }` pattern: guard on a certain condition, then use the results if that condition is true. v = f() if v: ...use v... invites injecting code in between the assignment and the test. They're two different things to the reader. And it's not as clear that `v` should only be used in the consequent body. if v := f(): ...use v... says exactly what it means: `f()` may return a truthy value. If it does, do something with it.

by pansa2 1y ago

almostgotcaught 1y ago

this has nothing to do with the walrus operator and everything to do with how string.format works in python https://docs.python.org/3/library/string.html#format-string-syntax https://docs.python.org/3/library/string.html#format-string-... Edit: someone downvoted me because they don't understand there is no walrus operator here print(f"{a:=10}")

lyu07282 1y ago
They obviously meant the second example: >>> print(f"{(a:=10)}")
- almostgotcaught 1y ago
  the output of the second example is "obvious" so i don't see the problem.
  - pansa2 1y ago
    Neither of the examples is problematic on its own; it's the fact that the language supports both of them. They're very hard to distinguish at-a-glance yet behave entirely differently.

sfink 1y ago

You can pry the walrus operator from my cold dead hands. m = re.match(pattern1, line) if m: do_stuff(m.group(1)) else: m = re.match(pattern2, line) if m: do_other_stuff(m.group(2)) else: m = re.match(pattern3, line) if m: do_things(m.groups()) else: m = ... Obviously, there are ways to improve this particular example without using the walrus. But it's also usually not this simple. I run into something like this all the time. Not many times per program, and I don't actually use the walrus all that often, but when it's the right thing it's so very nice.

marcosdumay 1y ago
You know, creating functions is allowed in Python. As are loops. The assignment is the least problematic thing on that code. I do even disagree on it being a problem.
callc 1y ago
Even though I’ve never used python walrus, I’m a huge fan of the “X language feature can be used as an expression” I feel the same way with rust control flow being used as an expression, and am disappointed when other languages don’t have it. Even though one could argue it makes things more complicated, I feel more mental freedom and feel the language getting out of the way.
pansa2 1y ago
The walrus operator hardly changes that example at all: if m := re.match(pattern1, line): do_stuff(m.group(1)) else: if m := re.match(pattern2, line): do_other_stuff(m.group(2)) else: if m := re.match(pattern3, line): do_things(m.groups()) else: m = ... I've found `:=` useful in the headers of `while` loops, but that's about it. The complexity that walrus adds to the language far outweighs its usefulness.
- ghewgill 1y ago
  The walrus operator allows you to use `elif` there to avoid cascading indentation. if m := re.match(pattern1, line): do_stuff(m.group(1)) elif m := re.match(pattern2, line): do_other_stuff(m.group(2)) elif m := re.match(pattern3, line): do_things(m.groups()) else: ...
  - pansa2 1y ago
    Ah, I missed that. Thanks
  - sfink 1y ago
    ...and for me, the benefit is that this is much more clear to me when reading the code. An increasing level of indentation directly maps to needing to keep more in my head. (Sure, in this case you can pattern match and see that there's nothing else, but in general you need to watch out for cases where the else may be doing more than just the next check on the same inputs. ) But the walrus is good even in the absence of a series of matches. It is quite common to need to know more than the boolean "did this match or not?", and so to my eye it is much cleaner to have one line doing the test and the next lines using the results. I don't care about saving characters or even lines. `m = ...match...` immediately followed by `if m:` feels like overhead for the sake of the programming language's limitations; it's extraneous to what I want to express. Also, I assert that the pattern is better for correctness. It's like Rust's `if let Some(foo) = f() { ... }` pattern: guard on a certain condition, then use the results if that condition is true. v = f() if v: ...use v... invites injecting code in between the assignment and the test. They're two different things to the reader. And it's not as clear that `v` should only be used in the consequent body. if v := f(): ...use v... says exactly what it means: `f()` may return a truthy value. If it does, do something with it.