I am running sage via virtual box and for some reason I am getting a syntax error for except. I was wondering if this wasn't available because I am using virtual box or if I am doing something wrong.
example below,
sage: def total_chromatic_number(G, certificate=False):
....: nmax = len(G) + len(G.edges()) # trivial upper bound on the number of colors.
....: for n in range(1,nmax+1):
....: p = MixedIntegerLinearProgram()
....: bv = p.new_variable(binary=True)
....: be = p.new_variable(binary=True)
....: for v in G.vertices():
....: p.add_constraint(sum(bv[v,c] for c in range(n)) == 1)
....: for e in G.edges(labels=False):
....: p.add_constraint(sum(be[e,c] for c in range(n)) == 1)
....: for v in G.vertices():
....: for c in range(n):
....: p.add_constraint(bv[v,c] + sum(be[e,c] for e in G.edges_incident(v, labels=False)) <= 1)
....: for v,w in G.edges(labels=False):
....: for c in range(n):
....: p.add_constraint(bv[v,c] + bv[w,c] + be[(v,w),c] <= 1)
....: try:
....: p.solve()
....: if certificate:
....: bv_sol = p.get_values(bv)
....: be_sol = p.get_values(be)
....: coloration = {}
....: for v in G.vertices():
....: for c in range(n):
....: if bv_sol[v,c] == 1:
....: coloration[v] = c
....: for e in G.edges(labels=False):
....: for c in range(n):
....: if be_sol[e,c] == 1:
....: coloration[e] = c
....: return coloration
....: else:
....: return n
....: except MIPSolverException:
File "<ipython-input-17-059a0ac5e5a6>", line 34
except MIPSolverException:
^
SyntaxError: invalid syntax
