# Query module - finally in trunk

Category: General, sympy, Tecnología

The query module is finally in the main SymPy repository. I made
substantial changes since last post, most of them at the user interface
level (thanks to Vinzent and Mateusz for many insightful comments). Main
function is ask(), which replaces the old expression.is_* syntax. You
can ask many things. For example, you can ask if a given expression is
integer, prime or real: [cc lang="python"] >>> ask(2, Q.integer) True
>>> ask(x**2, Q.integer) None >>> ask(x**2, Q.integer, Assume(x,
Q.integer)) True >>> ask(sqrt(2)*x, Q.integer, Assume(x, Q.integer))
>>> ask(I*x, Q.real, Assume(x, Q.imaginary)) True >>> ask(x*y,
Q.prime, Assume(x, Q.prime) & Assume(y, Q.prime)) False [/cc] as you
see, it returns True when it is sure that the expression is an integer,
None if it does not know, and False if it is certainly not an integer.
The second argument, which we will call 'key' specifies what we want to
ask about. For example, Q.integer ask wether expression is an integer,
Q.negative wether it's a negative, etc. For a complete list of all the
keys available, see doc/src/modules/queries.txt in sympy codebase. It
also accepts an optional third argument where you can specify
assumptions that symbols in expr satisfy. That can be any kind of
boolean expression involving assumptions, for example:
`Assume(x, Q.positive) & Assume(x, Q.integer)` or
`Assume(x, Q.positive) | Assume(x, Q.negative)`, or even
`NAnd(Assume(x, Q.positive), Assume(x, Q.integer)`