"%.2f" does not return a clean float. It returns a string representing this float with two decimals.
my_list = [0.30000000000000004, 0.5, 0.20000000000000001]
my_formatted_list = [ '%.2f' % elem for elem in my_list ]
returns:
['0.30', '0.50', '0.20']
Also, don’t call your variable list. This is a reserved word for list creation. Use some other name, for example my_list.
If you want to obtain [0.30, 0.5, 0.20] (or at least the floats that are the closest possible), you can try this:
my_rounded_list = [ round(elem, 2) for elem in my_list ]
returns:
[0.29999999999999999, 0.5, 0.20000000000000001]