Functional way to compare things inside a list

[88888 Dihedral]

Ulrich Eckhardt於 2012年9月21日星期五UTC+8下午5時15分03秒寫道：
> Am 21.09.2012 00:58, schrieb thorsopia at lavabit.com:
> 
> > list = [{'1': []}, {'2': []}, {'3': ['4', '5']}]
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> >
> 
> > I want to check for a value (e.g. '4'), and get the key of the dictionary
> 
> > that contains that value.
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> 
> 
> Note:
> 
> 1. list is a built-in type, who's name is rebound above
> 
> 2. The list above contains dictionaries that all only contain a single key?
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> 3. You have strings containing decimal representations of numbers?
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> 
> 
>  > (Yep, this is bizarre.)
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> 
> 
> The data are really stored in a strange way and you might be able to 
> 
> make things clearer by reorganizing them a bit.
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> 
> 
> 
> 
> > some_magic(list, '4')
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> > => '3'
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> >
> 
> > What's the functional way to do it?
> 
> 
> 
> Functional as in functional programming and an emphasis on lazy 
> 
> evaluation? In that case I'd write a generator that emits the keys where 
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> the values contain the requested string.
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> 
> 
> 
> 
> > Is it possible to do it with a one-liner?
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> 
> 
> Yep, filter(), lambda and the 'in' operator. Question remains if this is 
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> readable. Note that you can use a local function, too, if you just want 
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> to reduce the scope/visibility.
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> 
> 
> 
> 
> Good luck!
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> 
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> 
> 
> Uli

I don't think functional aspects are only marked as lazy
programming. 

It just means when one is experimenting something 
the efficient execution in speed is not on focus 
yet.