5 ms·

If anyone's looking for some more good WTFs in Python: https://github.com/satwikkansal/wtfpython https://github.com/satwikkansal/wtfpython

by Figs 6y ago

maxwelljoslyn 6y ago
Wow. (a) I don't know Python as well as I thought I did. (b) I suddenly never want to use it again. All these edge cases! All these behaviors, which I'm sure were added with the noble intention of increasing developer convenience, but which I'm equally sure have cost a larger amount of developer sanity!
- tziki 6y ago
  If you don't want to use a language because in theoretical scenarios it's possible construct unintuitive operations with it, then what language are you left with?
  - afandian 6y ago
    LISP?
  - tromp 6y ago
    I was going to bring up Haskell as a language with clear semantics, but even that has its quirks, like Prelude> [1, 3 .. 10] :: [Float] [1.0,3.0,5.0,7.0,9.0,11.0] In Haskell, this is syntactic sugar for the function enumFromThenTo (in typeclass Enum), which in my view should not have a special case implementation for Float.
- tyre 6y ago
  I've been writing python for about a year and change now (~7 years of engineering generally) and I never want to use it again. It feels to me like javascript in that it's "popular" because people already use/know it. So that huge existing codebase is the equivalent to the web; if you want to build on it, you're stuck with this. But my lord. Whitespace sensitivity is a terrible choice and there are piles of kludges trying to work around that. It means no multi-line lambdas so you end up with these unreadable list comprehensions `[ sub_item.value for sub_item in item.sub_items in items if item.is_the_best ]`. Lines copied into the console care about indentation which is definitely not a fun DX. Not to mention these random global functions everywhere. Whew. Mistakes were made.
  - andybak 6y ago
    > Whitespace sensitivity is a terrible choice It's my favourite feature of Python and I actively seek out other languages that make this terrible choice. I regularly use Python and a couple of curly brace languages and coming back to Python always feels like a breath of fresh air.
    - aib 6y ago
      > > Whitespace sensitivity is a terrible choice > It's my favourite feature of Python It's like the speed bump: It's for people who can't follow simple rules. It inconveniences you, but is rationalized with that it ultimately makes the world a little safer for everyone, including you. Me, I unindent temporary code like debug-print statements and literals overriding actual data. This makes it impossible to commit by accident. But my argument against whitespace sensitivity would be that bad and unreadable code is bad and unreadable regardless of its whitespace. In fact, force-formatting it just hides the evidence.
    - pansa2 6y ago
      > Python always feels like a breath of fresh air. That’s a good way to put it. Significant indentation makes the syntax so much more lightweight. This image [0] is supposed to be a joke, but to me it clearly demonstrates how braces and semicolons are both ugly and redundant. [0] https://www.reddit.com/r/ProgrammerHumor/comments/2wrxyt/ https://www.reddit.com/r/ProgrammerHumor/comments/2wrxyt/
  - pansa2 6y ago
    > It means no multi-line lambdas so you end up with these unreadable list comprehensions `[ sub_item.value for sub_item in item.sub_items in items if item.is_the_best ]` How would you rather write that code? Is it lack of multi-line lambdas that stops you from writing it as you would like?
    - deleted 6y ago
      [deleted]
    - ulucs 6y ago
wadkar 6y ago
Whooaaa! This is a gem and should be a handy reference to look up. I knew about the hash function, and how it generates same hash value for objects that have same numerical value. But it's so easy to forget!
DarthGhandi 6y ago
Wow, some of those entries are painful to read.
nickm12 6y ago
I must be a crusty Python programmer, because none of the first few examples seemed like WTFs to me at all. I think a WTF is when you think you know a language and then see something that behaves completely unlike how you expect.
- nolok 6y ago
  After seeing years / decade of such things about PHP, welcome to our world.
- ben509 6y ago
  I was annoyed by the number of RTFMs they call WTFs. They even claim some WTFs where Python behaves exactly as a naive user would expect, e.g. if I put 5 and 5.0 in a dict they are treated as the same key. I saw two valid ones: "Lossy zip of iterators" is because Python conflates iterables and iterators, "The disappearing variable from outer scope" where deleting the exception is contrary to how scope works everywhere else. They also miss the classic newbie head-scratcher: x = [] for i in range(10): x.append(lambda: i) x[0]()
- drusepth 6y ago
  I'd also classify WTFs as something that behaves completely unlike how you'd expect based on knowing many other similar/related languages, also.
stinos 6y ago
That thing is good, it's just a bit of a pitty the titles are so undescriptive. For example a typical one (in other languages as well) like a closed-over loop variable having the value of the last iteration in the closure, is called "the sticky output function". Meaning if this weren't all on one page it would be hard if not impossible to find what you're looking for.
giu 6y ago
>>> row = [""] * 3 #row i['', '', ''] >>> board = [row] * 3 >>> board[0][0] = "X" >>> board [['X', '', ''], ['X', '', ''], ['X', '', '']] I almost felt helpless for an hour when I used this list initialization [0] the first time in my code and couldn't find the reason why my unit tests where failing. [0] https://github.com/satwikkansal/wtfpython#-a-tic-tac-toe-where-x-wins-in-the-first-attempt https://github.com/satwikkansal/wtfpython#-a-tic-tac-toe-whe...

If anyone's looking for some more good WTFs in Python: https://github.com/satwikkansal/wtfpython https://github.com/satwikkansal/wtfpython

by Figs 6y ago

If anyone's looking for some more good WTFs in Python: https://github.com/satwikkansal/wtfpython https://github.com/satwikkansal/wtfpython

maxwelljoslyn 6y ago

Wow. (a) I don't know Python as well as I thought I did. (b) I suddenly never want to use it again. All these edge cases! All these behaviors, which I'm sure were added with the noble intention of increasing developer convenience, but which I'm equally sure have cost a larger amount of developer sanity!

tziki 6y ago
If you don't want to use a language because in theoretical scenarios it's possible construct unintuitive operations with it, then what language are you left with?
- afandian 6y ago
  LISP?
- tromp 6y ago
  I was going to bring up Haskell as a language with clear semantics, but even that has its quirks, like Prelude> [1, 3 .. 10] :: [Float] [1.0,3.0,5.0,7.0,9.0,11.0] In Haskell, this is syntactic sugar for the function enumFromThenTo (in typeclass Enum), which in my view should not have a special case implementation for Float.
tyre 6y ago
I've been writing python for about a year and change now (~7 years of engineering generally) and I never want to use it again. It feels to me like javascript in that it's "popular" because people already use/know it. So that huge existing codebase is the equivalent to the web; if you want to build on it, you're stuck with this. But my lord. Whitespace sensitivity is a terrible choice and there are piles of kludges trying to work around that. It means no multi-line lambdas so you end up with these unreadable list comprehensions `[ sub_item.value for sub_item in item.sub_items in items if item.is_the_best ]`. Lines copied into the console care about indentation which is definitely not a fun DX. Not to mention these random global functions everywhere. Whew. Mistakes were made.
- andybak 6y ago
  > Whitespace sensitivity is a terrible choice It's my favourite feature of Python and I actively seek out other languages that make this terrible choice. I regularly use Python and a couple of curly brace languages and coming back to Python always feels like a breath of fresh air.
  - aib 6y ago
    > > Whitespace sensitivity is a terrible choice > It's my favourite feature of Python It's like the speed bump: It's for people who can't follow simple rules. It inconveniences you, but is rationalized with that it ultimately makes the world a little safer for everyone, including you. Me, I unindent temporary code like debug-print statements and literals overriding actual data. This makes it impossible to commit by accident. But my argument against whitespace sensitivity would be that bad and unreadable code is bad and unreadable regardless of its whitespace. In fact, force-formatting it just hides the evidence.
  - pansa2 6y ago
    > Python always feels like a breath of fresh air. That’s a good way to put it. Significant indentation makes the syntax so much more lightweight. This image [0] is supposed to be a joke, but to me it clearly demonstrates how braces and semicolons are both ugly and redundant. [0] https://www.reddit.com/r/ProgrammerHumor/comments/2wrxyt/ https://www.reddit.com/r/ProgrammerHumor/comments/2wrxyt/
- pansa2 6y ago
  > It means no multi-line lambdas so you end up with these unreadable list comprehensions `[ sub_item.value for sub_item in item.sub_items in items if item.is_the_best ]` How would you rather write that code? Is it lack of multi-line lambdas that stops you from writing it as you would like?
  - deleted 6y ago
    [deleted]
  - ulucs 6y ago

wadkar 6y ago

Whooaaa! This is a gem and should be a handy reference to look up. I knew about the hash function, and how it generates same hash value for objects that have same numerical value. But it's so easy to forget!

DarthGhandi 6y ago

Wow, some of those entries are painful to read.

nickm12 6y ago

I must be a crusty Python programmer, because none of the first few examples seemed like WTFs to me at all. I think a WTF is when you think you know a language and then see something that behaves completely unlike how you expect.

nolok 6y ago
After seeing years / decade of such things about PHP, welcome to our world.
ben509 6y ago
I was annoyed by the number of RTFMs they call WTFs. They even claim some WTFs where Python behaves exactly as a naive user would expect, e.g. if I put 5 and 5.0 in a dict they are treated as the same key. I saw two valid ones: "Lossy zip of iterators" is because Python conflates iterables and iterators, "The disappearing variable from outer scope" where deleting the exception is contrary to how scope works everywhere else. They also miss the classic newbie head-scratcher: x = [] for i in range(10): x.append(lambda: i) x[0]()
drusepth 6y ago
I'd also classify WTFs as something that behaves completely unlike how you'd expect based on knowing many other similar/related languages, also.

stinos 6y ago

That thing is good, it's just a bit of a pitty the titles are so undescriptive. For example a typical one (in other languages as well) like a closed-over loop variable having the value of the last iteration in the closure, is called "the sticky output function". Meaning if this weren't all on one page it would be hard if not impossible to find what you're looking for.

giu 6y ago

>>> row = [""] * 3 #row i['', '', ''] >>> board = [row] * 3 >>> board[0][0] = "X" >>> board [['X', '', ''], ['X', '', ''], ['X', '', '']] I almost felt helpless for an hour when I used this list initialization [0] the first time in my code and couldn't find the reason why my unit tests where failing. [0] https://github.com/satwikkansal/wtfpython#-a-tic-tac-toe-where-x-wins-in-the-first-attempt https://github.com/satwikkansal/wtfpython#-a-tic-tac-toe-whe...