BUG,DOC,ENH,UBY: output lines are filtered by bool()

[westurner]

output text lines are filtered by bool(),
so, empty text lines (lines that do not contain a \n) are not filtered out, but e.g. an iterable with pyline.pyline that returns e.g. zero, [], () will be filtered out.

• (... see pandas for handling N/A, None)
• does this trim a blank trailing line ([...])?
  • echo -e '\n\n' | pyline.py prints two(+1 from echo) blank lines
  • echo -e '0' | pyline.py prints '0' (+1 blank line from echo) [because it's not casted to e.g. int]

[westurner]

• it may be helpful to add a filterfunc=bool kwarg and sensible CLI defaults for e.g. passing a callable that can return 0, None.

[westurner]

-O json may have different output characteristics (e.g. output everything as JSON) because this

[westurner]

Backwards-compatible:

• --no-strip-emptylines

Less surprising:

• --strip-emptylines

[westurner]

see also: #19