how to append to list in list comprehension

[Sayth Renshaw]

> > I want to go threw and for each index error at [4] append a 0.
> 
> You want to append 0 if the list does not have at least 5 items?
> 
> > p = re.compile('\d+')
> > fups = p.findall(nomattr['firstup'])
> > [x[4] for x in fups if IndexError fups.append(0)]
> > print(fups)
> 
> > Unsure why I cannot use append in this instance
> 
> Because that's incorrect syntax.
> 
> > how can I modify to acheive desired output?
> 
>     for f in fups:
>         if len(f) < 5:
>             f.append(0)
> 
> Or, if you really want to use a list comprehension:
> 
>       [f.append(0) for f in fups if len(f) < 5]
> 
> However there's no reason to use a list comprehension here.  The whole
> point of list comprehensions is to create a *new* list, which you don't
> appear to need; you just need to modify the existing fups list.
> 
> -- 
> John Gordon                   A is for Amy, who fell down the stairs
             B is for Basil, assaulted by bears
>                                 -- Edward Gorey, "The Gashlycrumb Tinies"

You are right John in that I don't want a new list I just wish to modify in-place to acheive the desired output.

I had no direct desire to use list comprehension just seemed an option.

Ultimately once it works I will abstract it into a function for other lists that will have a similar issue.

def listClean(fups)
    holder = [(f + ['0'] if len(f) < 5 else f) for f in fups ] 
    return holder[0], holder[1], holder[2], holder[3], holder[4]

and then call it in my csv.writer that I have, which currently errors quite correctly that it cannot write index[4] as some of my lists fail it.


I do like [(f + ['0'] if len(f) < 5 else f) for f in fups ] Rustom, if there are better non list comprehension options I would like to know as generally I find then confusing.
Cheers

Sayth