gistfile1.txt

>>> f1 = lambda i: '%s' % i
>>> f2 = lambda i: '%s'.format(i)
>>> import dis
>>> dis.dis(f1)
  1           0 LOAD_CONST               1 ('%s')
              3 LOAD_FAST                0 (i)
              6 BINARY_MODULO       
              7 RETURN_VALUE        
>>> dis.dis(f2)
  1           0 LOAD_CONST               1 ('%s')
              3 LOAD_ATTR                0 (format)
              6 LOAD_FAST                0 (i)
              9 CALL_FUNCTION            1
             12 RETURN_VALUE        
>>> f3 = lambda i: `i`
>>> dis.dis(f3)
  1           0 LOAD_FAST                0 (i)
              3 UNARY_CONVERT       
              4 RETURN_VALUE
>>> f4 = lambda i: str(i)
>>> dis.dis(f1)
  1           0 LOAD_GLOBAL              0 (str)
              3 LOAD_FAST                0 (i)
              6 CALL_FUNCTION            1
              9 RETURN_VALUE