@@ -754,6 +754,28 @@ def test_format(self):
754754        self .assertEqual (format (INF , 'f' ), 'inf' )
755755        self .assertEqual (format (INF , 'F' ), 'INF' )
756756
757+         # thousands separators 
758+         x  =  123_456.123_456 
759+         self .assertEqual (format (x , '_f' ), '123_456.123456' )
760+         self .assertEqual (format (x , ',f' ), '123,456.123456' )
761+         self .assertEqual (format (x , '._f' ), '123456.123_456' )
762+         self .assertEqual (format (x , '.,f' ), '123456.123,456' )
763+         self .assertEqual (format (x , '_._f' ), '123_456.123_456' )
764+         self .assertEqual (format (x , ',.,f' ), '123,456.123,456' )
765+         self .assertEqual (format (x , '.10_f' ), '123456.123_456_000_0' )
766+         self .assertEqual (format (x , '.10,f' ), '123456.123,456,000,0' )
767+         self .assertEqual (format (x , '>21._f' ), '       123456.123_456' )
768+         self .assertEqual (format (x , '<21._f' ), '123456.123_456       ' )
769+         self .assertEqual (format (x , '+.11_e' ), '+1.234_561_234_56e+05' )
770+         self .assertEqual (format (x , '+.11,e' ), '+1.234,561,234,56e+05' )
771+ 
772+         self .assertRaises (ValueError , format , x , '._6f' )
773+         self .assertRaises (ValueError , format , x , '.,_f' )
774+         self .assertRaises (ValueError , format , x , '.6,_f' )
775+         self .assertRaises (ValueError , format , x , '.6_,f' )
776+         self .assertRaises (ValueError , format , x , '.6_n' )
777+         self .assertRaises (ValueError , format , x , '.6,n' )
778+ 
757779    @support .requires_IEEE_754  
758780    def  test_format_testfile (self ):
759781        with  open (format_testfile , encoding = "utf-8" ) as  testfile :
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