class Solution(object):

def generate(self, numRows):

"""

:type numRows: int

:rtype: List[List[int]]

"""

if numRows == 0:

return []

pascal_triangle = [[1], [1,1]] # Constant values which are common for any pascal triangle

row = 2

while row < numRows:

previous = pascal_triangle[-1]

current = []

for i in range(len(previous)+1):

if i-1 < 0 or i+1 > len(previous):

current.append(1)

else:

current.append(previous[i]+previous[i-1])

pascal_triangle.append(current)

row += 1

return pascal_triangle[:numRows]