Using repr instead of str for parameters (not objects) for disambiguity
>>> for e in ( 0 , "0" , None , "None" , 1.23 , "1.23" , [ 1 , 2 ], { "foo" : "bar" }): ... print " %r " % e ... 0 '0' None 'None' 1.23 '1.23' [ 1 , 2 ] { 'foo' : 'bar' } When %s is used to interpolate to string there could be a bit of ambiguity introduced. >>> for e in ( 0 , "0" , None , "None" , 1.23 , "1.23" , [ 1 , 2 ], { "foo" : "bar" }): ... print " %s " % e ... 0 0 None None 1.23 1.23 [ 1 , 2 ] { 'foo' : 'bar' }