On Tue, Jan 13, 2009 at 12:02 AM, imageguy <imageguy1...@gmail.com> wrote: > Using py2.5.4 and entering the following lines in IDLE, I don't really > understand why I get the result shown in line 8. > > Note the difference between lines 7 and 10 is that 'else' clause > result enclosed in brackets, however, in line 2, both the 'c,d' > variables are assign correctly without the brackets being required. > > 1) >>> n = None > 2) >>> c,d = n if n is not None else 0,0 > 3) >>> print c,d, type(c), type(d) > 4) 0 0 <type 'int'> <type 'int'>
The ternary expression has higher precedence than the comma, so the actual effect of line 2 (and 8) is: >>> c, d = (n if n is not None else 0), 0 Or written more explicitly: >>> c = n if n is not None else 0 >>> d = 0 So the only correct way to write the expression, for the result you want, is to use your line 10: > 10) >>> c,d = n if n is not None else (0,0) But if you're struggling with the precedence issues, I'd recommend ditching ternary expressions altogether and using full conditional blocks. -Miles -- http://mail.python.org/mailman/listinfo/python-list
