why Lists in a class were changed without my operate? - python-3.x

Question

i run a class in a for cycle.
the code is:
graph_all = []
graph_now = graph_exc(-1)
for lin in res_str:
if lin.strip():
print(lin)
if lin[0] == 't' :
if graph_now.numbering != (-1) :
graph_all.append(graph_now)
graph_now = graph_exc(int(lin[4:-1]))
if lin[0] == 'v' :
graph_now.add_vertex(lin[2],lin[4])
if lin[0] == 'e' :
graph_now.add_edges(lin[2],lin[4],lin[6])
else:
continue
res_str is a list full of sentences.
I use graph_all to accommdate all the class.
when the first letter is 'v' or 'e',i put something in graph_now's lists.
when the first letter is 't',i put graph_now to graph_all and re-define the graph_all.but i find a problem:when i define graph_all again,the lists in class in graph_all will be nothing,too!
the code of graph_exc is :
class graph_exc:
edges_on_1 = []
edges_on_2 = []
edges_on_edges = []
vertex_on = {}
def __init__(self,numbering):
self.num_edge = 0
self.num_vertex = 0
self.numbering = numbering
self.edges_on_edges.clear()
self.edges_on_2.clear()
self.edges_on_1.clear()
self.vertex_on.clear()
def add_vertex(self,ver,ver_num):
self.vertex_on[ver] = ver_num
self.num_vertex += 1
def add_edges(self,point_1,edges,point_2):
self.edges_on_1.append(point_1)
self.edges_on_edges.append(edges)
self.edges_on_2.append(point_2)
self.num_edge += 1
the problem is : edges_on_1,edges_on_edges,edges_on_2 and vertex will be influenced.the data in here will disappear.but the num_edge and num_vertex are not.
I try to use deepcopy method to solve it.but it does not work.