Here's a function that will do the trick:
def myformat(x):
return ('%.2f' % x).rstrip('0').rstrip('.')
And here are your examples:
>>> myformat(1.00)
'1'
>>> myformat(1.20)
'1.2'
>>> myformat(1.23)
'1.23'
>>> myformat(1.234)
'1.23'
>>> myformat(1.2345)
'1.23'
Edit:
From looking at other people's answers and experimenting, I found that g does all of the stripping stuff for you. So,
'%.3g' % x
works splendidly too and is slightly different from what other people are suggesting (using '{0:.3}'.format() stuff). I guess take your pick.