[Tutor] Loop optimization

[Kent Johnson]

wormwood_3 wrote:
> I ran a few tests, with the following results:
> 
> 1. Timing using the time module:
>        * Using for loop, src code:
>                     import time
>                     start = time.time()
>                     for word in self.dictcontents:
>                         self.potdomains.append(word + suffix1)
>                         self.potdomains.append(word + suffix2)
>                     end = time.time()
>                     runtime =  end - start
>                     print "Using time(), for loop took %s s" % runtime
> 
>         ** I obtained the following results (using the full agid-4 dictionary, ~112K entries):
>         python domainspotter.py --file resources/agid-4/infl.txt 
>         Using time(), for loop took 0.132480859756 s
>         python domainspotter.py --file resources/agid-4/infl.txt 
>         Using time(), for loop took 0.143032073975 s
>         python domainspotter.py --file resources/agid-4/infl.txt 
>         Using time(), for loop took 0.135424137115 s
> 
>        * Using generator, src code:
>             def suffixGen(self, words):
>                 suffix1 = ".com"
>                 suffix2 = ".net"
>                 for word in words:
>                     yield word + suffix1
>                     yield word + suffix2
>             def domainify(self):
>                 self.potdomains = []
>                 words = self.dictcontents
>                 import time
>                 start = time.time()
>                 self.potdomains = list(CheckDomains.suffixGen(self, words))
>                 end = time.time()
>                 runtime =  end - start
>                 print "Using time(), generator took %s s" % runtime
> 
>         ** I obtained the following results (using the full agid-4 dictionary, ~112K entries):
>         python domainspotter.py --file resources/agid-4/infl.txt 
>         Using time(), generator took 0.0830721855164 s
>         python domainspotter.py --file resources/agid-4/infl.txt 
>         Using time(), generator took 0.0818212032318 s
>         python domainspotter.py --file resources/agid-4/infl.txt 
>         Using time(), generator took 0.0830278396606 s
> 
> 
> This revealed that the generator seemed to be much faster, around 60% faster. 

You should try an optimized for loop:
                     append_ = self.potdomains.append_
                     s1_ = suffix1
                     s2_ = suffix2
                     for word in self.dictcontents:
                         append_(word + s1_)
                         append_(word + s2_)

This will take out some of the difference at least.

Note that if you are using this as part of your domainspotter project 
and you will be running a whois request on each of these names, any time 
you save in this loop will be completely overshadowed by the time for 
the whois request. So in this case the 'best' loop is probably the most 
readable one, not the one that shaves .05 seconds off the running time.

It's still fun to play with optimization, but don't take it too 
seriously until you know it will make a difference in the final program.

Kent