Hi!
Can somebody explain me this strange behavior of Sage :
for p in range(1,10):
for q in range(1,10):
print p/q
Then p/q return the integer division.
However:
for p in range(1,10):
print p/7
give rational results.
A solution is to use Rational(p)/Rational(q) instead of p/q. But it is not an explanation.
Thanks,
Arnaud
Ah! This is because range(1,10) is a pure Python command and so returns Python ints. Which, as we are using Python 2, return like this.
sage: preparser(False)
sage: 1/2
0
sage: preparser(True)
sage: 1/2
1/2
But once you use p/7, Sage's preparser says "That's the rational number p/7" and so does this correctly.
sage: preparse('p/7')
'p/Integer(7)'
A better solution is to use srange, which always uses Sage types if it can.
sage: srange(1,10)
[1, 2, 3, 4, 5, 6, 7, 8, 9]
sage: [type(i) for i in srange(1,10)]
[<type 'sage.rings.integer.Integer'>,
<type 'sage.rings.integer.Integer'>,
<type 'sage.rings.integer.Integer'>,
<type 'sage.rings.integer.Integer'>,
<type 'sage.rings.integer.Integer'>,
<type 'sage.rings.integer.Integer'>,
<type 'sage.rings.integer.Integer'>,
<type 'sage.rings.integer.Integer'>,
<type 'sage.rings.integer.Integer'>]
Asked: 2016-01-27 20:12:43 +0100
Seen: 471 times
Last updated: Jan 28 '16
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In working with Sage you have to know if you are dealing with a Sage integer or Python integer. They behave differently. Use srange as indicated in answer below. See also, this similar post