Buggy python submission (verdict: Runtime Error):
H, W = (int(i) for i in input().split())
t = []
t.append(['.']*(H+2))

for j in range(H):
	tmp = input()
	tmp = '.' + tmp + '.'
	t.append(list(tmp))

t.append(['.']*(H+2))

def CheckBlock(i,k):
	if t[i][k-1] == '#': #check up
		return 0
	elif t[i-1][k] == '#': #check left
		return 1
	elif t[i+1][k] == '#': #check right
		return 2
	elif t[i][k+1] == '#': #check down
		return 3
	else:
		return 4

for i in range(1,W+1):
	for k in range(1,H+1):
		if t[i][k] == '#':
			marker = CheckBlock(i,k)
			if marker == 4:
				print('No')
				quit()
print('Yes')

Fixed submission:
H, W = (int(i) for i in input().split())
t = []
t.append(['.']*(H+2))

for j in range(H):
	tmp = input()
	tmp = '.' + tmp + '.'
	t.append(list(tmp))

t.append(['.']*(H+2))

def CheckBlock(i,k):
	if t[i][k-1] == '#': #check up
		return 0
	elif t[i-1][k] == '#': #check left
		return 1
	elif t[i+1][k] == '#': #check right
		return 2
	elif t[i][k+1] == '#': #check down
		return 3
	else:
		return 4

for k in range(1,W+1):
	for i in range(1,H+1):
		if t[i][k] == '#':
			marker = CheckBlock(i,k)
			if marker == 4:
				print('No')
				quit()
print('Yes')

Buggy python submission (verdict: Runtime Error):
H, W = (int(i) for i in input().split())
t = []
t.append(['.']*(H+2))

for j in range(H):
	tmp = input()
	tmp = '.' + tmp + '.'
	t.append(list(tmp))

t.append(['.']*(H+2))

def CheckBlock(i,k):
	if t[i][k-1] == '#': #check up
		return 0
	elif t[i-1][k] == '#': #check left
		return 1
	elif t[i+1][k] == '#': #check right
		return 2
	elif t[i][k+1] == '#': #check down
		return 3
	else:
		return 4

for i in range(1,W+1):
	for k in range(1,H+1):
		if t[i][k] == '#':
			marker = CheckBlock(i,k)
			#ChangeBlock(i,k,marker)
			if marker == 4:
				print('No')
				quit()
print('Yes')

Fixed submission:
H, W = (int(i) for i in input().split())
t = []
t.append(['.']*(H+2))

for j in range(H):
	tmp = input()
	tmp = '.' + tmp + '.'
	t.append(list(tmp))

t.append(['.']*(H+2))

def CheckBlock(i,k):
	if t[i][k-1] == '#': #check up
		return 0
	elif t[i-1][k] == '#': #check left
		return 1
	elif t[i+1][k] == '#': #check right
		return 2
	elif t[i][k+1] == '#': #check down
		return 3
	else:
		return 4

for k in range(1,W+1):
	for i in range(1,H+1):
		if t[i][k] == '#':
			marker = CheckBlock(i,k)
			if marker == 4:
				print('No')
				quit()
print('Yes')

Buggy python submission (verdict: Runtime Error):
H, W = (int(i) for i in input().split())
t = []
t.append(['.']*(H+2))

for j in range(H):
	tmp = input()
	tmp = '.' + tmp + '.'
	t.append(list(tmp))

t.append(['.']*(H+2))


def issharp(block):
	if block == '#':
		return True
	else: return False

def CheckBlock(i,k):
#   0
# 1 X 2
#   3
	if t[i][k-1] == '#': #check up
		return 0
	elif t[i-1][k] == '#': #check left
		return 1
	elif t[i+1][k] == '#': #check right
		return 2
	elif t[i][k+1] == '#': #check down
		return 3
	else:
		return 4

for i in range(1,W+1):
	for k in range(1,H+1):
		if issharp(t[i][k]) == True:
			marker = CheckBlock(i,k)
			if marker == 4:
				print('No')
				quit()
print('Yes')

Fixed submission:
H, W = (int(i) for i in input().split())
t = []
t.append(['.']*(H+2))

for j in range(H):
	tmp = input()
	tmp = '.' + tmp + '.'
	t.append(list(tmp))

t.append(['.']*(H+2))

def CheckBlock(i,k):
	if t[i][k-1] == '#': #check up
		return 0
	elif t[i-1][k] == '#': #check left
		return 1
	elif t[i+1][k] == '#': #check right
		return 2
	elif t[i][k+1] == '#': #check down
		return 3
	else:
		return 4

for k in range(1,W+1):
	for i in range(1,H+1):
		if t[i][k] == '#':
			marker = CheckBlock(i,k)
			if marker == 4:
				print('No')
				quit()
print('Yes')