CSV with comments

[John Machin]

On 19/07/2006 5:34 AM, skip at pobox.com wrote:
>     >> In csv.reader, is there any way of skip lines that start whith '#' or
>     >> empty lines
> 
> Nope.  When we wrote the module we weren't aware of any "spec" that
> specified comments or blank lines.  You can easily write a file wrapper to
> filter them out though:
> 
>     class BlankCommentCSVFile:
>         def __init__(self, fp):
>             self.fp = fp
> 
>         def __iter__(self):
>             return self
> 
>         def next(self):
>             line = self.fp.next()
>             if not line.strip() or line[0] == "#":
>                 return self.next()

This is recursive. Unlikely of course, but if the file contained a large 
number of empty lines, might this not cause the recursion limit to be 
exceeded?


>             return line
> 
> Use it like so:
> 
>     reader = csv.reader(BlankCommentCSVFile(open("somefile.csv")))
>     for row in reader:
>         print row
> 

Hi Skip,

Is there any reason to prefer this approach to Daniel's, apart from 
being stuck with an older (pre-yield) version of Python?

A file given to csv.reader is supposed to be opened with "rb" so that 
newlines embedded in data fields can be handled properly, and also 
(according to a post by Andrew MacNamara (IIRC)) for DIY emulation of 
"rU". It is not apparent how well this all hangs together when a filter 
is interposed, nor whether there are any special rules about what the 
filter must/mustn't do. Perhaps a few lines for the docs?

Cheers,
John