How to format a float with a maximum number of decimal places and without extra zero padding?

What you’re asking for should be addressed by rounding methods like the built-in round function. Then let the float number be naturally displayed with its string representation.

>>> round(65.53, 4)  # num decimal <= precision, do nothing
'65.53'
>>> round(40.355435, 4)  # num decimal > precision, round
'40.3554'
>>> round(0, 4)  # note: converts int to float
'0.0'