Animate plot of two piecewise functions

edit

Consider a slightly modified version to the workaround to this question

sage: k = 5
sage: f = Piecewise([[(-2,1),k],[(1,4),x]])
sage: g =  Piecewise([[(-2,1),1],[(1,4),2*x]])
sage: P = plot(f,color='green')
sage: Q = plot(g,linestyle='--')
sage: P+Q

Is it possible to animate this plot say with k ranging from 0 to 10?

I tried:

k = 5
f = Piecewise([[(-2,1),k],[(1,4),x]])
g =  Piecewise([[(-2,1),1],[(1,4),2*x]])
P = plot(f,color='green')
Q = plot(g,linestyle='--')
X = P+Q
b = animate([X for k in srange(0,10)],xmin=0,xmax=4,figsize=[5,5])
b
b.show()

but it calculates for minutes and doesn't show up a result. (I tried examples from the documentation which worked fine).

I also tried this:

t = var('t')
k = var('k')

def f(t,k):
    if t <=1:
        return t
    else:
        return k


def g(t,k):
    if t <=1:
        return 1
    else:
        return 2*t

@interact
def _(k=(0,10)):
    p1=plot(f(t,k),(t,0,3),ymax=10,ymin=0,color='green')
    p2=plot(g(t,k),(t,0,3))
    show(p1 + p2)

However the piecewise defined functions don't work in this case.