still thinking about this stuff.
At 01:19 07.06.2003 +0200, Samuele Pedroni wrote:
>I thought python-dev archives would be a better place for this than my hd.
>Warning: terse.
>
>I have come to the conclusion that I should agree with Guido:
>
>- generators do not let really abstract over things like exception
>handling etc.
what I had in mind were generators like this one:
def all_lines(file_list_filename):
for fn in open(file_list_filename,'r'):
fn = fn.rstrip()
for line in open(fn,'r'):
yield line
for line in all_lines("all_files"):
<do-stuff>
what if we want to release resources (here in this toy example namely close
files) in a timely fashion in face of exception also in <do-stuff>.
all of these touch on the issue:
- non-support of 'yield' inside try-finally
- PEP 288: Generators Attributes and Exceptions
- PEP 310: Reliable Acquisition/Release Pairs
- proposals for syntax extensibility through Ruby/Smalltalk-like
first-class blocks
so all these proposals should be considered together and in an organic way.
With current Python a possible rewrite of the above would be:
class all_lines(object):
def __init__(self,file_list_fname):
self.listf = open(file_list_fname,'r')
self.f = None
def __iter__(self):
for fn in self.listf:
fn = fn.rstrip()
self.f = open(fn,'r')
for line in self.f:
yield line
self.f.close()
self.f = None
def close(self):
self.listf.close()
if self.f: self.f.close()
x = all_lines("all_files")
try:
for line in x:
<do-stuff>
finally:
x.close()
kind of obfuscated.
maybe-generators-should-grow-a-close-method-ly y'rs - Samuele
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