Format a number containing a decimal point with leading zeroes

Question

I want to format a number with a decimal point in it with leading zeros.

This

>>> '3.3'.zfill(5)
003.3

considers all the digits and even the decimal point. Is there a function in python that considers only the whole part?

I only need to format simple numbers with no more than five decimal places. Also, using %5f seems to consider trailing instead of leading zeros.