On Tue, 15 Mar 2005 22:45:48 -0700, Steven Bethard wrote:
> # table as default argument value so you don't have to do
> # a global lookup each time it's used
>
> def show(seq, table=string.maketrans('ACBDGHK\nMNSRUTWVY',
> 'TGVHCDM\nKNSYAAWBR')
> seq = seq.upper().translate(table)[::-1]
> # print string in slices of length 60
> for i in range(0, len(seq), 60):
> print seq[i:i+60]
>
> def main():
> seq = []
> # alias methods to avoid repeated lookup
> join = ''.join
> append = seq.append
> for line in sys.stdin:
> # note only one "line[0]" by using "in" test
> if line[0] in ';>':
> # note no need to check if seq is empty; show now prints
> # nothing for an empty string
> show(join(seq))
> print line,
> del seq[:]
> else:
> append(line[:-1])
>
Wow - that ran about 10 times faster on a 10MB input file. The significant
change was the for loop inside the show function: your method avoids the
increment and if statement and of course has 60x fewer iterations total.
> reversed() won't save you any memory -- you're already loading the
> entire string into memory anyway.
>
>
> Interesting tidbit:
> del seq[:]
> tests faster than
> seq = []
>
> $ python -m timeit -s "lst = range(1000)" "lst = []"
> 10000000 loops, best of 3: 0.159 usec per loop
>
> $ python -m timeit -s "lst = range(1000)" "del lst[:]"
> 10000000 loops, best of 3: 0.134 usec per loop
>
> It's probably the right way to go in this case anyway -- no need to
> create a new empty list each time.
Fascinating - I hadn't thought about that.
Besides redoing that loop, the remaining optimizations produce less than a
10% speed-up; in particular, adding the function aliases increases the
number of lines of code (another benchmark in the shootout), and I would
imagine that the organizers don't really want that type of special
optimization (no developer is going to write that in their programs
unless they have really time-critical code, so this is the sort of hit
that Python really should take in the contest as penalty for being so
dynamically nifty ;)). So here's a tentative contest version of the code:
import sys
import string
def show(seq, table=string.maketrans('ACBDGHK\nMNSRUTWVYacbdghkmnsrutwvy',
'TGVHCDM\nKNSYAAWBRTGVHCDMKNSYAAWBR')):
seq = seq.translate(table)[::-1]
for i in range(0, len(seq), 60):
print seq[i:i+60]
def main():
seq = []
for line in sys.stdin:
if line[0] in ';>':
show(''.join(seq))
print line,
del seq[:]
else:
seq.append(line[:-1])
show(''.join(seq))
main()
--
Jacob Lee
[EMAIL PROTECTED] | www.nearestneighbor.net
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