5 ms·

What exactly would people do with multi-line lambdas? I would definitely refactor any lambda with statements or more than one expression in it, give it a name,

What exactly would people do with multi-line lambdas? I would definitely refactor any lambda with statements or more than one expression in it, give it a name, or use a list comprehension, so I've never seen a problem with them. Can anybody give me an example of a piece of code they think would look better if python had multi-line lambdas?

rw 17y ago
If you give something a name, yet still only use it once, what's the point? It is just semantic clutter to do that (unless, of course, you can't use multiline lambdas...).
- CaptSolo 17y ago
  There is no big harm in giving something a name. Giving a name also helps if you find a need to reuse it later. Plus a name can give a hint to what this code is for.
  - rw 17y ago
    Yet, if you look in functional programming code (e.g. Haskell, Scheme), you'll find many anonymous lambdas (that in python would be > 1 line). Why would good coders bother doing that?
    - eru 17y ago
      If something is small and enough to be anonymous, it's usually simply enough to be expressed without binding a variable. (See point-free style.)
      - rw 17y ago
        Obviously. Show us how to do point-free style in Python. We're talking about Python's lame implementation of anonymous functions, not something that it doesn't have any implementation of.
        eru 17y ago
        Oh, I thought you were talking about programmers' habits in Haskell.
- GeneralMaximus 17y ago
  In Python, you can easily define methods within methods, so there is little semantic clutter at the toplevel. def doSomething(): def doSomethingElse(): # Code goes here. pass eggs = filter(doSomethingElse, spam) for cheese in eggs: # Do something. pass
hedgehog 17y ago
Those are just two of the complaints I hear most. A friend of mine actually went so far as to patch Python to use curly braces at the start of a project in Python. "Perfect Python" he called it. Personally I think deviating from PEP8 & standard idioms is likely to cause more pain in maintainability than you win in elegant syntax.
- dkersten 17y ago
  Ugh, he means imperfect python, right? Even if I hated the indention sytnax, which I dont (and it seems to me that it grows on most people after a few weeks of use), I think a patched python is the wrong way to go about it as you now deviate from the main python distributions, so cant make use of updates and bugfixes (and do all libraries play nice with a patched version? maybe - maybe not). If you absolutely must have braces, use #{ and #} :-D, you should be indenting anyway! I really don't get why some people hate the indention-as-syntax. Sure, its different to C and Java, but it also results in (more) consistently formatted code and readable indention. It also only takes a day or two to get used to, even if you're a hardened C++ user (for the record, I have nothing against C/C++ syntax, I actually switched from years of C++ to Python as my main language and I just recently started a C++/Python hybrid project).
gaius 17y ago
Because functional languages discourage loops. This is just a really trivial example, but: # value x =[|1;2;3;4|]; value x : array int = [|1; 2; 3; 4|] # for i = 0 to (Array.length x) - 1 do { Printf.printf "%d" x.(i); }; 1234- : unit = () # Array.iter (fun y -> Printf.printf "%d" y) x; 1234- : unit = () Basically the entire body of any for loop I would want to make an anonymous function. Then if I cared about the result I could do: # Array.map (fun y -> Printf.printf "%d" y) x; 1234- : array unit = [|(); (); (); ()|] Assuming the underlying platform supported it, and the function is pure, that's "free" parallelism.

rw 17y ago

If you give something a name, yet still only use it once, what's the point? It is just semantic clutter to do that (unless, of course, you can't use multiline lambdas...).

CaptSolo 17y ago
There is no big harm in giving something a name. Giving a name also helps if you find a need to reuse it later. Plus a name can give a hint to what this code is for.
- rw 17y ago
  Yet, if you look in functional programming code (e.g. Haskell, Scheme), you'll find many anonymous lambdas (that in python would be > 1 line). Why would good coders bother doing that?
  - eru 17y ago
    If something is small and enough to be anonymous, it's usually simply enough to be expressed without binding a variable. (See point-free style.)
    - rw 17y ago
      Obviously. Show us how to do point-free style in Python. We're talking about Python's lame implementation of anonymous functions, not something that it doesn't have any implementation of.
      - eru 17y ago
        Oh, I thought you were talking about programmers' habits in Haskell.
GeneralMaximus 17y ago
In Python, you can easily define methods within methods, so there is little semantic clutter at the toplevel. def doSomething(): def doSomethingElse(): # Code goes here. pass eggs = filter(doSomethingElse, spam) for cheese in eggs: # Do something. pass

hedgehog 17y ago

Those are just two of the complaints I hear most. A friend of mine actually went so far as to patch Python to use curly braces at the start of a project in Python. "Perfect Python" he called it. Personally I think deviating from PEP8 & standard idioms is likely to cause more pain in maintainability than you win in elegant syntax.

dkersten 17y ago
Ugh, he means imperfect python, right? Even if I hated the indention sytnax, which I dont (and it seems to me that it grows on most people after a few weeks of use), I think a patched python is the wrong way to go about it as you now deviate from the main python distributions, so cant make use of updates and bugfixes (and do all libraries play nice with a patched version? maybe - maybe not). If you absolutely must have braces, use #{ and #} :-D, you should be indenting anyway! I really don't get why some people hate the indention-as-syntax. Sure, its different to C and Java, but it also results in (more) consistently formatted code and readable indention. It also only takes a day or two to get used to, even if you're a hardened C++ user (for the record, I have nothing against C/C++ syntax, I actually switched from years of C++ to Python as my main language and I just recently started a C++/Python hybrid project).

gaius 17y ago

Because functional languages discourage loops. This is just a really trivial example, but: # value x =[|1;2;3;4|]; value x : array int = [|1; 2; 3; 4|] # for i = 0 to (Array.length x) - 1 do { Printf.printf "%d" x.(i); }; 1234- : unit = () # Array.iter (fun y -> Printf.printf "%d" y) x; 1234- : unit = () Basically the entire body of any for loop I would want to make an anonymous function. Then if I cared about the result I could do: # Array.map (fun y -> Printf.printf "%d" y) x; 1234- : array unit = [|(); (); (); ()|] Assuming the underlying platform supported it, and the function is pure, that's "free" parallelism.