Using enumerate to get line-numbers with itertools grouper?

Terry Reedy tjreedy at
Wed Sep 2 19:48:31 CEST 2015

On 9/2/2015 6:04 AM, Victor Hooi wrote:
> I'm using grouper() to iterate over a textfile in groups of lines:
> def grouper(iterable, n, fillvalue=None):
>      "Collect data into fixed-length chunks or blocks"
>      # grouper('ABCDEFG', 3, 'x') --> ABC DEF Gxx
>      args = [iter(iterable)] * n
>      return zip_longest(fillvalue=fillvalue, *args)
> However, I'd also like to know the line-number that I'm up to, for printing out in informational or error messages.
> Is there a way to use enumerate with grouper to achieve this?

Without a runnable test example, it is hard to be sure what you want. 
However, I believe replacing 'iter(iterable)' with 'enumerate(iterable, 
1)', and taking into account that you will get (line_number, line) 
tuples instead of lines, will do what you want.

Terry Jan Reedy

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