Weird result returned from adding floats depending on order I add them

[joanne matthews (RRes-Roth)]

I'm getting different results when I add up a list of floats depending
on the order that I list the floats. For example, the following returns
False:
def check():
        totalProp=0
        inputs=[0.2,0.2,0.2,0.1,0.2,0,0.1]
        for each in inputs:
        
                totalProp+=each
        print "totalProp=",totalProp
        if totalProp != 1:
                print "Your proportions must add up to 1"
   
                return False
        return True

However, if I swap, the 4th and 5th list items like this:

totalProp=0
inputs=[0.2,0.2,0.2,0.2,0.1,0,0.1]
for each in inputs:
        
   totalProp+=each
   print "totalProp=",totalProp
   if totalProp != 1:
        print "Your proportions must add up to 1"
   
        return False
   return True

I get True returned. Can anyone tell me whats going on and how I can
avoid the problem. Thanks

Joanne Matthews
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