Paul Rubin wrote:
> In the course of writing a bunch of generator-oriented code I kept
> wanting to temporarily truncate the output of generators for debugging,
> i.e. I might have a function like
>
> def generate_bazillion_items():
> for line in bazillion_line_file:
> yield itemify(line)
>
> where I wanted to test the program on just the first 20 lines of the
> file. After a number of rounds of editing the program to wrap an
> xrange(20) loop I went to using islice(bazillion_line_file, 20), but
> even more handy was to write this decorator:
>
> def truncate(n):
> from itertools import islice
> def trunc(gen): # truncate generator to n items
> return lambda *a,**kw: islice(gen(*a,**kw), n)
> return trunc
>
> Then to chop bazillion_items to 20 items, I just write:
>
> @truncate(20)
> def generate_bazillion_items():
> for line in bazillion_line_file:
> yield itemify(line)
>
> When I want to run the whole file, I comment out the @truncate line,
> and if I want to debug again, I just uncomment it.
Thes may be overkill, but how about allowing None as a parameter to
truncate, to allow for programmatic truncation?
# top of module
if DEBUG:
FILETRUNC = 20
else:
FILETRUNC = None
# imported, etc.
def truncate(n):
if n is None:
return lambda gen: gen
from itertools import islice
def trunc(gen): # truncate generator to n items
return lambda *a,**kw: islice(gen(*a,**kw), n)
return trunc
# in the body somewhere
@truncate(FILETRUNC)
def generate_bazillion_items():
# etc.
James
--
http://mail.python.org/mailman/listinfo/python-list
