[Alex Martelli]
> On Sunday 02 February 2003 11:04 pm, Samuele Pedroni wrote:
> > With Guido's 'do': [notice that count is rebindable in the thunk]
> >
> > class iterclose:
> > def __init__(self,iterwclose):
> > self.iter = iterwclose
> >
> > def __call__(self,thunk):
> > try:
> > for x in self.iter:
> > thunk(x)
> > finally:
> > self.iter.close()
> >
> > count = 0
> > do iterclose(open('blah.txt')): (line):
> > if line.find('Python') >=0:
> > count += 1
> > print line,
>
> OK -- I *don't* get that " (line):" part, and how calling thunk() in
> iterclose.__init__ binds/rebinds the local (?) variable line of the thunk.
> Looks like black magic to me. Guess I must just be a bit thick
> tonight -- sorry.
>
After staring at this for a minute I figured out what ``(line):`` does.
So what you have to realize is that the block (from ``if line...`` to
``print line,`` is passed into ``__call__()`` and bound to ``thunk()``.
Now the object bound to ``thunk`` accepts a single argument, named
``line`` in ``thunk``. In ``__call__()`` the variable ``x`` is what is
being passed into the thunk code and being bound to ``line``. Phew. =)
So, to make sure I am not confuing myself, ``do`` does the
following:
Instantiates ``iterclose(open('blah.txt'))``.
Compiles the block of code that makes up the thunk.
It ends up accepting a single argument which bound to ``line``.
Calls ``iterclose().__call__(<thunk>)`` and executes it.
We all let our heads stop spinning from all that and have a good, stiff
drink. =)
-Brett
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