Buggy python submission (verdict: Runtime Error):
if __name__ == "__main__":
    H, W = map(int, input().split())
    s = []
    for i in range(H):
        s.append(input())
    
    """
    # black
    . white
    """
    
    black = "#"
    white = "."
    
    ans = "Yes"
    break_flag = False
    for i in range(H):
        for j in range(W):
            if s[i][j] == black:
                above = False
                under = False
                left = False
                right = False
                
                if 0 < i:
                    above = (s[i - 1][j] == black)
                if i < W - 1:
                    under = (s[i + 1][j] == black)
                if 0 < j:
                    left = (s[i][j - 1] == black)
                if j < H - 1:
                    right = (s[i][j + 1] == black)
                
                if not (above or under or left or right):
                    break_flag = True
                    ans = "No"
                    #print(i, j)
                    #print(above, under, left, right)
            
            if break_flag:
                break
            
        if break_flag:
            break
    
    print(ans)

Fixed submission:
if __name__ == "__main__":
    H, W = map(int, input().split())
    s = []
    for i in range(H):
        s.append(input())
    
    """
    # black
    . white
    """
    
    black = "#"
    white = "."
    
    ans = "Yes"
    break_flag = False
    for i in range(H):
        for j in range(W):
            if s[i][j] == black:
                above = False
                under = False
                left = False
                right = False
                
                if 0 < i:
                    above = (s[i - 1][j] == black)
                if i < H - 1:
                    under = (s[i + 1][j] == black)
                if 0 < j:
                    left = (s[i][j - 1] == black)
                if j < W - 1:
                    right = (s[i][j + 1] == black)
                
                if not (above or under or left or right):
                    break_flag = True
                    ans = "No"
                    #print(i, j)
                    #print(above, under, left, right)
            
            if break_flag:
                break
            
        if break_flag:
            break
    
    print(ans)

Buggy python submission (verdict: Runtime Error):
if __name__ == "__main__":
    H, W = map(int, input().split())
    s = []
    for i in range(H):
        s.append(input())
    
    """
    # black
    . white
    """
    
    black = "#"
    white = "."
    
    ans = "Yes"
    break_flag = False
    for i in range(H):
        for j in range(W):
            if s[i][j] == black:
                above = False
                under = False
                left = False
                right = False
                
                if 0 < i:
                    above = (s[i - 1][j] == black)
                if i < W - 1:
                    under = (s[i + 1][j] == black)
                if 0 < j:
                    left = (s[i][j - 1] == black)
                if j < W - 1:
                    right = (s[i][j + 1] == black)
                
                if not (above or under or left or right):
                    break_flag = True
                    ans = "No"
                    #print(i, j)
                    #print(above, under, left, right)
            
            if break_flag:
                break
            
        if break_flag:
            break
    
    print(ans)

Fixed submission:
if __name__ == "__main__":
    H, W = map(int, input().split())
    s = []
    for i in range(H):
        s.append(input())
    
    """
    # black
    . white
    """
    
    black = "#"
    white = "."
    
    ans = "Yes"
    break_flag = False
    for i in range(H):
        for j in range(W):
            if s[i][j] == black:
                above = False
                under = False
                left = False
                right = False
                
                if 0 < i:
                    above = (s[i - 1][j] == black)
                if i < H - 1:
                    under = (s[i + 1][j] == black)
                if 0 < j:
                    left = (s[i][j - 1] == black)
                if j < W - 1:
                    right = (s[i][j + 1] == black)
                
                if not (above or under or left or right):
                    break_flag = True
                    ans = "No"
                    #print(i, j)
                    #print(above, under, left, right)
            
            if break_flag:
                break
            
        if break_flag:
            break
    
    print(ans)

Buggy python submission (verdict: Runtime Error):
if __name__ == "__main__":
    H, W = map(int, input().split())
    s = []
    for i in range(H):
        s.append(input())
    
    """
    # black
    . white
    """
    
    black = "#"
    white = "."
    
    ans = "Yes"
    break_flag = False
    for i in range(H):
        for j in range(W):
            if s[i][j] == black:
                above = False
                under = False
                left = False
                right = False
                
                if 0 < i:
                    above = (s[i - 1][j] == black)
                if i < W - 1:
                    under = (s[i + 1][j] == black)
                if 0 < j:
                    left = (s[i][j - 1] == black)
                if j < W - 1:
                    right = (s[i][j + 1] == black)
                
                if not (above or under or left or right):
                    break_flag = True
                    ans = "No"
                    #print(i, j)
                    #print(above, under, left, right)
            
            if break_flag:
                break
            
        if break_flag:
            break
    
    print(ans)

Fixed submission:
if __name__ == "__main__":
    H, W = map(int, input().split())
    s = []
    for i in range(H):
        s.append(input())
    
    """
    # black
    . white
    """
    
    black = "#"
    white = "."
    
    ans = "Yes"
    break_flag = False
    for i in range(H):
        for j in range(W):
            if s[i][j] == black:
                above = False
                under = False
                left = False
                right = False
                
                if 0 < i:
                    above = (s[i - 1][j] == black)
                if i < H - 1:
                    under = (s[i + 1][j] == black)
                if 0 < j:
                    left = (s[i][j - 1] == black)
                if j < W - 1:
                    right = (s[i][j + 1] == black)
                
                if not (above or under or left or right):
                    break_flag = True
                    ans = "No"
                    #print(i, j)
                    #print(above, under, left, right)
            
            if break_flag:
                break
            
        if break_flag:
            break
    
    print(ans)