Re-write a few un-Pythonic lines

[clintval]

• self.__dict__.get(attr)
  

  sample-sheet/sample_sheet/_sample_sheet.py

  Line 259 in 87deb18

  return self.__dict__.get(attr, None)

• There must be a better way to change a class name without needing useless inheritance
  

  sample-sheet/sample_sheet/_sample_sheet.py

  Lines 320 to 325 in 87deb18

  	class Header(SampleSheetSection):
  	pass
  	class Settings(SampleSheetSection):
  	pass

• return None if len(self.Reads) == 0 else len(self.Reads) == 1
  

  sample-sheet/sample_sheet/_sample_sheet.py

  Lines 437 to 439 in 87deb18

  	if len(self.Reads) == 0:
  	return None
  	return len(self.Reads) == 1

• VALID_ASCII = {string.ascii_letters + string.digits + '-_'}
  

  sample-sheet/sample_sheet/_sample_sheet.py

  Lines 31 to 36 in 87deb18

  	VALID_ASCII_CODES = [
  	10,
  	13,
  	32,
  	*list(range(33, 47)),
  	*list(range(48, 127))]

[PertuyF]

A few suggestions/remarks:

self.__dict__.get(attr)

you can use collections.defaultdict(lambda: None) to achieve the same behavior as self.get(attr, None). But after looking to the code, I'm not sure why you need to overload __dict__.

change a class name

seems that you don't need that at all, just use

self.header = SampleSheetSection()

in SampleSheet's __init__

None if len(self.Reads) == 0

return None if not self.Reads else len(self.Reads) == 1

will do, as bool(iterable) will return False only if the iterable is empty.

[clintval]

Fixed in PR #24