dropping trailing ‘.0’ from floats

See PEP 3101:

'g' - General format. This prints the number as a fixed-point
      number, unless the number is too large, in which case
      it switches to 'e' exponent notation.

Old style (not preferred):

>>> "%g" % float(10)
'10'

New style:

>>> '{0:g}'.format(float(21))
'21'

New style 3.6+:

>>> f'{float(21):g}'
'21'