what list comprehension can't

[Steven D'Aprano]

On Fri, 24 Jun 2005 21:04:15 +0200, Christophe Delord wrote:

> Hello,
> 
> On 24 Jun 2005 11:45:14 -0700, ajikoe at gmail.com wrote:
> 
>> Hello,
>> 
>> Can we impose if then else into list comprehension ?
>> Like we do in lambda-map form:
>> 
>> This code change None into 0
>> L = [None, 12]
>> R = map(lambda x: (x==None and [0] or x)[0], L) # [0,12]
>> 
> 
> Do you mean:
>    [(x==None and [0] or [x])[0] for x in L]
> or [{None:0}.get(x,x) for x in L]
> or [x or 0 for x in L]
> 
> Well, the third solution doesn't exactly fit the specification but may
> be easier to read.

Or, more generally, 

[0 for x in L if x is None]

which doesn't solve the asked-for question, but is a useful feature.


-- 
Steven.