Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3

import sys

sys.setrecursionlimit(1000000)

N, M = [int(x) for x in input().split()]

# D[i][j]: Card i has a rel. with card j
D = [[] for i in range(N)]
for i in range(M):
    x, y, z = [int(x) for x in input().split()]
    x -= 1
    y -= 1
    D[x].append(y)
    D[y].append(x)

visited = [False for i in range(N)]
def dfs(n):
    for idx in D[n]:
        if not visited[idx]:
            visited[idx] = True
            dfs(idx)

cnt = 0
for n in range(N):
    if not visited[n]:
        visited[n] = True
        dfs(n)
        cnt += 1
print(cnt)


Fixed submission:
#!/usr/bin/env python3

import sys

sys.setrecursionlimit(1000000)

N, M = [int(x) for x in input().split()]

# D[i][j]: Card i has a rel. with card j
D = [[] for i in range(N)]
for i in range(M):
    x, y, z = [int(x) for x in input().split()]
    x -= 1
    y -= 1
    D[x].append(y)
    D[y].append(x)

visited = [False for i in range(N)]
def dfs(n):
    for idx in D[n]:
        if not visited[idx]:
            visited[idx] = True
            dfs(idx)

cnt = 0
for n in range(N):
    if not visited[n]:
        visited[n] = True
        dfs(n)
        cnt += 1
print(cnt)

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3

#import numpy as np
#import scipy, scipy.special

# Python 3 modules: https://docs.python.org/3/library/

import sys
import math, itertools, operator
from math import *
from math import factorial as fact
from itertools import permutations, combinations
from functools import reduce
# Use scipy for stats: https://docs.scipy.org/doc/scipy/reference/stats.html
# Before Python 3.5
from fractions import gcd

inf = float('inf')

def lcm(a, b):
    return a * b // gcd(a,b)

def perm(a, b):
    import scipy.special
    return scipy.special.perm(a, b, exact = True)

def comb(a, b):
    import scipy.special
    return scipy.special.comb(a, b, exact = True)

def dfact(n):
    import scipy.special
    return scipy.special.factorial2(n, exact = True)

def prod(l):
    return reduce(operator.mul, l)

def input_ints(inp = input, sep = ' ', conv = int):
    return map(conv, inp().split(sep = sep))

################################################################################

sys.setrecursionlimit(1000000)

N, M = input_ints()

# D[i][j]: Card i has a rel. with card j
D = [[] for i in range(N)]
for i in range(M):
    x, y, z = input_ints()
    x -= 1
    y -= 1
    D[x].append(y)
    D[y].append(x)

visited = [False for i in range(N)]
def dfs(n):
    for idx in D[n]:
        if not visited[idx]:
            visited[idx] = True
            dfs(idx)

cnt = 0
for n in range(N):
    if not visited[n]:
        visited[n] = True
        dfs(n)
        cnt += 1
print(cnt)


Fixed submission:
#!/usr/bin/env python3

import sys

sys.setrecursionlimit(1000000)

N, M = [int(x) for x in input().split()]

# D[i][j]: Card i has a rel. with card j
D = [[] for i in range(N)]
for i in range(M):
    x, y, z = [int(x) for x in input().split()]
    x -= 1
    y -= 1
    D[x].append(y)
    D[y].append(x)

visited = [False for i in range(N)]
def dfs(n):
    for idx in D[n]:
        if not visited[idx]:
            visited[idx] = True
            dfs(idx)

cnt = 0
for n in range(N):
    if not visited[n]:
        visited[n] = True
        dfs(n)
        cnt += 1
print(cnt)

Buggy python submission (verdict: Runtime Error):
#!/usr/bin/env python3

#import numpy as np
#import scipy, scipy.special

# Python 3 modules: https://docs.python.org/3/library/

import sys
import math, itertools, operator
from math import *
from math import factorial as fact
from itertools import permutations, combinations
from functools import reduce
# Use scipy for stats: https://docs.scipy.org/doc/scipy/reference/stats.html
# Before Python 3.5
from fractions import gcd

inf = float('inf')

def lcm(a, b):
    return a * b // gcd(a,b)

def perm(a, b):
    import scipy.special
    return scipy.special.perm(a, b, exact = True)

def comb(a, b):
    import scipy.special
    return scipy.special.comb(a, b, exact = True)

def dfact(n):
    import scipy.special
    return scipy.special.factorial2(n, exact = True)

def prod(l):
    return reduce(operator.mul, l)

def input_ints(inp = input, sep = ' ', conv = int):
    return map(conv, inp().split(sep = sep))

################################################################################

sys.setrecursionlimit(20000)

N, M = input_ints()

# D[i][j]: Card i has a rel. with card j
D = [[] for i in range(N)]
for i in range(M):
    x, y, z = input_ints()
    x -= 1
    y -= 1
    D[x].append(y)
    D[y].append(x)

visited = [False for i in range(N)]
def dfs(n):
    for idx in D[n]:
        if not visited[idx]:
            visited[idx] = True
            dfs(idx)

cnt = 0
for n in range(N):
    if not visited[n]:
        visited[n] = True
        dfs(n)
        cnt += 1
print(cnt)


Fixed submission:
#!/usr/bin/env python3

import sys

sys.setrecursionlimit(1000000)

N, M = [int(x) for x in input().split()]

# D[i][j]: Card i has a rel. with card j
D = [[] for i in range(N)]
for i in range(M):
    x, y, z = [int(x) for x in input().split()]
    x -= 1
    y -= 1
    D[x].append(y)
    D[y].append(x)

visited = [False for i in range(N)]
def dfs(n):
    for idx in D[n]:
        if not visited[idx]:
            visited[idx] = True
            dfs(idx)

cnt = 0
for n in range(N):
    if not visited[n]:
        visited[n] = True
        dfs(n)
        cnt += 1
print(cnt)