[Tutor] replacing a loop

[Peter Otten]

johnf wrote:

> Hi folks,
> 
> 
> I have the following loop (actually repeated many times )

If you have repetetive code look into ways to parameterize it, like

def choices(rows, choices_column, keys_column):
    ...

> 
> def locChoices(self):
>  locDS = self.eslocation.getDataSet()
>  loc_Choices=['<None>']
>  locKeys=[0]
>  for row in locDS:
>  loc_Choices.append(row['facility'])
>  locKeys.append(row['pkid'])
> 
> return loc_Choices,locKeys
> 
> where locDS is a tuple of dicts and a row is a dict.
> 
> Since I use a lot of similar loops to populate many dropdown controls I
> started investigating the use of list comprehensions.  But I can't
> figure out how to use them in this loop 

You need two loops in this case

choices = ["<None>"] + [row["facility"] for row in ds]
keys = [0] + [row["pkid"] for row in ds]

> and wonder if it will improve
> the performance. 

No, list comprehensions are unlikely to improve performance.

> The data is not very big - about a thousand rows -
> give or take.
> 
> So what do you guys think?

Are you sure (aka: did you measure that) building these lists takes a 
significant amount of time?
If there is a GUI involved any delay you notice is more likely to stem from 
filling the widgets than from preparing the lists.