Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

class UnionFind:
    def __init__(self, N):
        # negative value: represents the root of a tree; its absolute value is the size of the tree
        # positive value: the parent's index
        self.vertices = [-1 for _ in range(N)]
        self.rank = [0] * N
        
    def find(self, v):
        if self.vertices[v] < 0: # v is a root
            return v
        else:
            # path compression: reconnect v to the root
            self.vertices[v] = self.find(self.vertices[v])
            return self.vertices[v]
        
    def union(self, u, v):
        s1 = self.find(u) # the root of the tree including vertex u
        s2 = self.find(v) # the root of the tree including vertex v
        
        if s1 == s2: # u and v is in the same tree
            return False
        
        if self.rank[s1] > self.rank[s2]: # the tree including u is taller
            self.vertices[s1] += self.vertices[s2] # update the size of the bigger tree
            self.vertices[s2] = s1
        else: # the tree including v is taller
            self.vertices[s2] += self.vertices[s1] # update the size of the bigger tree
            self.vertices[s1] = s2
            if self.rank[s1] == self.rank[s2]:
                self.rank[s2] += 1
        return True
        
    def is_connected(self, u, v):
        return self.find(u) == self.find(v)
    
    def size(self, v):
        return -self.vertices[self.find(v)]

N, K, L = map(int, input().split())
road = UnionFind(N)
rail = UnionFind(N)
for _ in range(K):
    p, q = map(int, input().split())
    road.union(p-1, q-1)
for _ in range(L):
    r, s = map(int, input().split())
    rail.union(r-1, s-1)
cnct_road = defaultdict(list)
cnct_rail = defaultdict(list)
for i in range(N):
    cnct_road[road.find(i)].append(i)
    cnct_rail[rail.find(i)].append(i)
ans = []
for i in range(N):
    ro = set(cnct_road[road.find(i)])
    ra = set(cnct_rail[rail.find(i)])
    ans.append(len(ro & ra))
print(*ans)

Fixed submission:
from collections import defaultdict

class UnionFind:
    def __init__(self, N):
        # negative value: represents the root of a tree; its absolute value is the size of the tree
        # positive value: the parent's index
        self.vertices = [-1 for _ in range(N)]
        self.rank = [0] * N
        
    def find(self, v):
        if self.vertices[v] < 0: # v is a root
            return v
        else:
            # path compression: reconnect v to the root
            self.vertices[v] = self.find(self.vertices[v])
            return self.vertices[v]
        
    def union(self, u, v):
        s1 = self.find(u) # the root of the tree including vertex u
        s2 = self.find(v) # the root of the tree including vertex v
        
        if s1 == s2: # u and v is in the same tree
            return False
        
        if self.rank[s1] > self.rank[s2]: # the tree including u is taller
            self.vertices[s1] += self.vertices[s2] # update the size of the bigger tree
            self.vertices[s2] = s1
        else: # the tree including v is taller
            self.vertices[s2] += self.vertices[s1] # update the size of the bigger tree
            self.vertices[s1] = s2
            if self.rank[s1] == self.rank[s2]:
                self.rank[s2] += 1
        return True
        
    def is_connected(self, u, v):
        return self.find(u) == self.find(v)
    
    def size(self, v):
        return -self.vertices[self.find(v)]

N, K, L = map(int, input().split())
road = UnionFind(N)
rail = UnionFind(N)
for _ in range(K):
    p, q = map(int, input().split())
    road.union(p-1, q-1)
for _ in range(L):
    r, s = map(int, input().split())
    rail.union(r-1, s-1)
comp = defaultdict(int)
tpls = []
for i in range(N):
    t = (road.find(i), rail.find(i))
    comp[t] += 1
    tpls.append(t)
print(*[comp[t] for t in tpls])

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

class UnionFind:
    def __init__(self, N):
        # negative value: represents the root of a tree; its absolute value is the size of the tree
        # positive value: the parent's index
        self.vertices = [-1 for _ in range(N)]
        self.rank = [0] * N
        
    def find(self, v):
        if self.vertices[v] < 0: # v is a root
            return v
        else:
            # path compression: reconnect v to the root
            self.vertices[v] = self.find(self.vertices[v])
            return self.vertices[v]
        
    def union(self, u, v):
        s1 = self.find(u) # the root of the tree including vertex u
        s2 = self.find(v) # the root of the tree including vertex v
        
        if s1 == s2: # u and v is in the same tree
            return False
        
        if self.rank[s1] > self.rank[s2]: # the tree including u is taller
            self.vertices[s1] += self.vertices[s2] # update the size of the bigger tree
            self.vertices[s2] = s1
        else: # the tree including v is taller
            self.vertices[s2] += self.vertices[s1] # update the size of the bigger tree
            self.vertices[s1] = s2
            if self.rank[s1] == self.rank[s2]:
                self.rank[s2] += 1
        return True
        
    def is_connected(self, u, v):
        return self.find(u) == self.find(v)
    
    def size(self, v):
        return -self.vertices[self.find(v)]

N, K, L = map(int, input().split())
road = UnionFind(N)
rail = UnionFind(N)
for _ in range(K):
    p, q = map(int, input().split())
    road.union(p-1, q-1)
for _ in range(L):
    r, s = map(int, input().split())
    rail.union(r-1, s-1)
cnct_road = defaultdict(list)
cnct_rail = defaultdict(list)
for i in range(N):
    cnct_road[road.find(i)].append(i)
    cnct_rail[rail.find(i)].append(i)
ans = []
for i in range(N):
    ro = set(cnct_road[road.find(i)])
    ra = set(cnct_rail[rail.find(i)])
    ans.append(len(ro & ra))
print(*ans)

Fixed submission:
from collections import defaultdict

class UnionFind:
    def __init__(self, N):
        # negative value: represents the root of a tree; its absolute value is the size of the tree
        # positive value: the parent's index
        self.vertices = [-1 for _ in range(N)]
        self.rank = [0] * N
        
    def find(self, v):
        if self.vertices[v] < 0: # v is a root
            return v
        else:
            # path compression: reconnect v to the root
            self.vertices[v] = self.find(self.vertices[v])
            return self.vertices[v]
        
    def union(self, u, v):
        s1 = self.find(u) # the root of the tree including vertex u
        s2 = self.find(v) # the root of the tree including vertex v
        
        if s1 == s2: # u and v is in the same tree
            return False
        
        if self.rank[s1] > self.rank[s2]: # the tree including u is taller
            self.vertices[s1] += self.vertices[s2] # update the size of the bigger tree
            self.vertices[s2] = s1
        else: # the tree including v is taller
            self.vertices[s2] += self.vertices[s1] # update the size of the bigger tree
            self.vertices[s1] = s2
            if self.rank[s1] == self.rank[s2]:
                self.rank[s2] += 1
        return True
        
    def is_connected(self, u, v):
        return self.find(u) == self.find(v)
    
    def size(self, v):
        return -self.vertices[self.find(v)]

N, K, L = map(int, input().split())
road = UnionFind(N)
rail = UnionFind(N)
for _ in range(K):
    p, q = map(int, input().split())
    road.union(p-1, q-1)
for _ in range(L):
    r, s = map(int, input().split())
    rail.union(r-1, s-1)
comp = defaultdict(int)
tpls = []
for i in range(N):
    t = (road.find(i), rail.find(i))
    comp[t] += 1
    tpls.append(t)
print(*[comp[t] for t in tpls])