Float + min/max?

[Shu-Hsien Sheu]

Hi,

I am new to Python, and just wrote a small program to generate the maximum
number of the cartisian coordinates among all atoms in a given molecule.
However, I found the float function, if combined with max function, to be
kind of confusing. It would give a number with uneccessary decimals from
nowhere.

Not converting to float:

x = []
for i in (0, length-2):
    slines[i] =  lines[i].split()
    if slines[i][0] == "ATOM":
        x.append(slines[i][6])

print "xmax = " + max(x) + "  " + "xmin = " + min(x)

Output:
xmax = 90.179  xmin = 64.112


Converting to float numbers:

x = []
for i in (0, length-2):
    slines[i] =  lines[i].split()
    if slines[i][0] == "ATOM":
        x.append( float(slines[i][6]) )

print "xmax = " + max(x) + "  " + "xmin = " + min(x)

Output:
xmax = 90.179000000000002  xmin = 64.111999999999995


The original data file apparantly does not have those decimals. May I ask
how does it happend? Thank!

-shuhsien