input: Write a function to print out Pascal's triangle for a given number of rows. If the number of rows is less than or equal to 0, the function should print nothing.
  def pascal_triangle(n): 
      trow = [1] 
      y = [0] 
      for x in range(max(n, 0)): 
          print(trow) 
          trow=[l+r for l,r in zip(trow + y, y + trow)] 
      return n>=1
  
  assert pascal_triangle(5)==True
  assert pascal_triangle(0)==False
  assert pascal_triangle(-3)==False
output: def pascal_triangle(n): 
      if n <= 0: 
          return False
      trow = [1] 
      y = [0] 
      for x in range(n): 
          print(trow) 
          trow=[l+r for l,r in zip(trow + y, y + trow)] 
      return True