On Sat, Oct 23, 2010 at 8:07 PM, Jason Grout <[email protected]> wrote: > A correction to my corrections inline below! > > On 10/23/10 9:56 PM, Jason Grout wrote: >> >> A few little corrections or explanations inline below... >> >> On 10/23/10 8:34 AM, Francois Maltey wrote: >>> >>> Rolandb wrote : >>>> >>>> test=((k2,k1) for k1 in xrange(2,4) for k2 in xrange(1,k1) if >>>> gcd(k1,k2)==1) >>>> print [t for t in test] >>>> print [t for t in test] >>>> [(1, 2), (1, 3), (2, 3)] >>>> [] >>>> >>> I begun to confuse lists L with [...] we can free change : >>> one change one term by L[1]=123, and change the length by >>> L[3:4]=[7,6,8], or del, or L.pop(), ... >>> And tuple with (...) as T=(12,13,14,15) it's impossible to change. >>> >>> A void tuple or a void list are [] and () >> >> Actually, the empty tuple is (,)---you mention why in this next sentence: >> > > You were right and I was wrong! > > sage: type(()) > <type 'tuple'> > sage: (,) > ------------------------------------------------------------ > File "<ipython console>", line 1 > (,) > ^ > SyntaxError: invalid syntax
In most cases, it's really the comma (not the parentheses) that creates the tuple. sage: a = 123, sage: a (123,) The parentheses are often needed for grouping purposes though. - Robert -- To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
