This is a substitution. `subs` will replace symbols in an expression with
different expressions. The syntax is `expr.subs(old, new)` or
`expr.subs({oldi: newi})` or `expr.subs([(old1, new1), (old2, new2),
...])`. You can read about the different forms with `help(Expr.subs)`.
>>> eqs = Eq(a, x + y), Eq(b, x*y)
Examples of converting eqs to dict or list for subs
>>> dict([i.args for i in eqs])
{a: x + y, b: x*y}
>>> [i.args for i in eqs]
[(a, x + y), (b, x*y)]
Using one of those forms to do the substitution:
>>> (a*b).subs(_)
x*y*(x + y)
On Monday, July 8, 2019 at 9:11:37 PM UTC-5, Gary Pajer wrote:
>
> I'm sure I'm not the first person having trouble getting started. If
> there is a good tutorial, more detailed than the sympy docs tutorial,
> please point me to it!
>
> I want to display the product of two expressions. Suppose I have
>
> a, b, x, y = symbols('a b x y')
> ex1 = Eq(a, x + y)
> ex2 = Eq(b, x * y)
>
> How do I display a * b in terms of x and y?
>
> Thainks.
>
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