Python pattern printing--Christmas tree

# 提示用户需要打印的层数
layer = int(input("请输入需要打印的层数： "))

for i in range(1, layer + 1):
	space_num = layer - i
	start_num = 2 * i -1
	for j in range(space_num):
		print(" ",end="")
	for j in range(start_num):
		print("*",end="")
	print()

for i in range(layer + 1):
	for j in range((2 * layer - 1) // 2):

		print(" ",end = "")
	print("*")