[Tutor] lambdas, generators, and the like

[Dave Angel]

 Keith Winston <keithwins at gmail.com> Wrote in message:
> I've got this line:
> 
> for k in range(len(tcombo)):
>     tcombo_ep.append(list(combinations(tcombo, k+1)))
> 
> generating every possible length combination of tcombo. I then test
> them, and throw most of them away. I need to do this differently, it
> gets way too big (crashes my computer).
> 
You should learn how to write and use a generator. Anytime you
 find yourself creating a huge list, and only navigating it once, 
 consider writing a generator instead. A generator is any function
 that has a yield in it. You can turn the loop above into a
 one-level generator by

def gen (tcombo):
    for k in range (len (tcombo))
          yield list (combinations (tcombo, k+1))

And depending how you use the nested list, remove the call to list
 () for some real serious space savings. 

(untested)



> any help will be appreciated. I don't really understand lambda
> functions yet, but I can sort of imagine they might work here
> somehow... or not.
> 
A lambda is seldom necessary or useful in simple programs. 
> 


-- 
DaveA nr



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