Martin Walsh wrote:
> def addcommas(f):
> """
> This amounts to reversing everything left
> of the decimal, grouping by 3s, joining
> with commas, reversing and reassembling.
> """
> # assumes type(f) == float
> left, right = ('%0.2f' % f).split('.')
> rleft = [left[::-1][i:i+3] for i in range(0, len(left), 3)]
> return ','.join(rleft)[::-1] + '.' + right
def addcommas(s): # assumes type(s)==str
b=[]
l=len(s)
for i,v in enumerate(s):
i+=1 # easier to understand w/ 1-based indexing, i think.
b.append(v)
if (l-i)%3==0 and not i==l:
b.append(',')
return ''.join(b)
or, somewhat more tersely:
def addcommas2(s):
l=len(s)
return ''.join(v+',' if (l-(i+1))%3==0 and not i+1-l==0
else v for i,v in enumerate(s))
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