4 ms·

In all seriousness, the only reason I use Python over Lua is for the library. Lua is far more flexible and extensible, but it has a very sore lack of standard

In all seriousness, the only reason I use Python over Lua is for the library. Lua is far more flexible and extensible, but it has a very sore lack of standard libraries like you can find with Python. But I keep my fingers crossed, and continue to use Lua as an interpreter inside my C apps, where the lack of libraries is a non-issue because everything I need to use is a custom API exported from C.

silentbicycle 18y ago
> but it has a very sore lack of standard libraries like you can find with Python Agreed. I find it quite a bit more elegant overall, and I decided to just jump in and do my throwaway scripts in Lua and see how much of a difference that makes. If I like it enough to write a few small libraries along the way, everybody wins. Lua has tail-call elimination, coroutines, closures, and lambdas. I'm pretty sure Python has none of these, except for (possibly) a limited form of coroutines. (The Python lambda is too crippled, its closures are broken.) Lua is also one of the most deliberately portable languages I've seen, too. I have a hunch it would be a great language for bootstrapping a Lisp or Scheme compiler, though I haven't tried this yet.
- eru 18y ago
  Python closures work well. (The lambda is syntactically crippled.)
  - silentbicycle 18y ago
    >>> def makeAdder(x): def inc(y): return y+x return inc >>> f = makeAdder(3) >>> f(4) 7 So far, so good. >>> def makeAdder2(x): v = x def inc(y): v += y return v return inc >>> f2 = makeAdder2(3) >>> f2(4) Traceback (most recent call last): File "<pyshell#15>", line 1, in <module> f2(4) File "<pyshell#13>", line 4, in inc v += y UnboundLocalError: local variable 'v' referenced before assignment >>> It looks like you can't mutate variables in a closure. Am I doing it wrong? If you really can't, that seriously limits their power. -- In Lua: > function adder(x) local v = x function inc(y) v = v + y return v end return inc end >> >> >> >> >> >> >> > f = adder(3) > =f(4) 7 > =f(4) 11 > =f(4) 15 > Works fine. (Also, the syntax is really clean.)
    - eru 18y ago
      You may need to add a 'global' statement or something similiar. If you are going to mutate a variable in a function Python assumes that you want to create a new variable in that scope. Generally I do not mutate variables as far as possible, so I have not hit this problem myself, yet. Perhaps there is someone more knowledgeable about Python to step in.
      - silentbicycle 18y ago
        But it's not a global variable, it's scoped within the closure. So, this means Python doesn't have lexical scoping?
        eru 18y ago
        It has. Just the syntax was a bit awkward when modifying variables of higher scope. See sibling comment.
    - EliAndrewC 18y ago
      Python 3.0 fixes this with the nonlocal statement. However, you are correct that this doesn't work in Python 2.5 and earlier.
      - silentbicycle 18y ago
        Ok, thanks.
    - anamax 18y ago
      Argh - I can't get the formatting to work. def makeAdder2(x): v = [x,] def inc(y): v[0] += y return v[0] return inc works just fine in all pythons with closures (2.0 and above?) def makeAdder2(x): def inc(y, v=[x,]): v[0] += y return v[0] return inc Also works and provides a mechanism for resetting the state.
      - silentbicycle 18y ago

silentbicycle 18y ago

> but it has a very sore lack of standard libraries like you can find with Python Agreed. I find it quite a bit more elegant overall, and I decided to just jump in and do my throwaway scripts in Lua and see how much of a difference that makes. If I like it enough to write a few small libraries along the way, everybody wins. Lua has tail-call elimination, coroutines, closures, and lambdas. I'm pretty sure Python has none of these, except for (possibly) a limited form of coroutines. (The Python lambda is too crippled, its closures are broken.) Lua is also one of the most deliberately portable languages I've seen, too. I have a hunch it would be a great language for bootstrapping a Lisp or Scheme compiler, though I haven't tried this yet.

eru 18y ago
Python closures work well. (The lambda is syntactically crippled.)
- silentbicycle 18y ago
  >>> def makeAdder(x): def inc(y): return y+x return inc >>> f = makeAdder(3) >>> f(4) 7 So far, so good. >>> def makeAdder2(x): v = x def inc(y): v += y return v return inc >>> f2 = makeAdder2(3) >>> f2(4) Traceback (most recent call last): File "<pyshell#15>", line 1, in <module> f2(4) File "<pyshell#13>", line 4, in inc v += y UnboundLocalError: local variable 'v' referenced before assignment >>> It looks like you can't mutate variables in a closure. Am I doing it wrong? If you really can't, that seriously limits their power. -- In Lua: > function adder(x) local v = x function inc(y) v = v + y return v end return inc end >> >> >> >> >> >> >> > f = adder(3) > =f(4) 7 > =f(4) 11 > =f(4) 15 > Works fine. (Also, the syntax is really clean.)
  - eru 18y ago
    You may need to add a 'global' statement or something similiar. If you are going to mutate a variable in a function Python assumes that you want to create a new variable in that scope. Generally I do not mutate variables as far as possible, so I have not hit this problem myself, yet. Perhaps there is someone more knowledgeable about Python to step in.
    - silentbicycle 18y ago
      But it's not a global variable, it's scoped within the closure. So, this means Python doesn't have lexical scoping?
      - eru 18y ago
        It has. Just the syntax was a bit awkward when modifying variables of higher scope. See sibling comment.
  - EliAndrewC 18y ago
    Python 3.0 fixes this with the nonlocal statement. However, you are correct that this doesn't work in Python 2.5 and earlier.
    - silentbicycle 18y ago
      Ok, thanks.
  - anamax 18y ago
    Argh - I can't get the formatting to work. def makeAdder2(x): v = [x,] def inc(y): v[0] += y return v[0] return inc works just fine in all pythons with closures (2.0 and above?) def makeAdder2(x): def inc(y, v=[x,]): v[0] += y return v[0] return inc Also works and provides a mechanism for resetting the state.
    - silentbicycle 18y ago