dirknbr wrote:
Hi
I have 2 files (done and outf), and I want to chose unique elements
from the 2nd column in outf which are not in done. This code works but
is not efficient, can you think of a quicker way? The a=1 is just a
redundant task obviously, I put it this way around because I think
'in' is quicker than 'not in' - is that true?
done_={}
for line in done:
done_[line.strip()]=0
print len(done_)
universe={}
for line in outf:
if line.split(',')[1].strip() in universe.keys():
a=1
else:
if line.split(',')[1].strip() in done_.keys():
a=1
else:
universe[line.split(',')[1].strip()]=0
Dirk
Where you have a=1, one would normally use the "pass" statement. But
you're wrong that 'not in' is less efficient than 'in'. If there's a
difference, it's probably negligible, and almost certainly less than the
extra else clause you're forcing here.
When doing an 'in', do *not* use the keys() method, as you're replacing
a fast lookup with a slow one, not to mention the time it takes to build
the keys() list each time.
In both these cases, you can use a set, rather than a dict. And there's
no need to test whether the item is already in the set, just put it in
again.
Changing all that, you'll wind up with something like (untested)
done_set = set()
universe = set()
for line in done:
done_set.add(line.strip())
for line in outf:
item = line.split(',')[1].strip()
if item not in done_set
universe.add(item)
DaveA
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