上下对称的杨辉三角形

生成上下对称的杨辉三角形

* 
* * 
* * * 
* * * * 
* * * * * 
* * * * 
* * * 
* * 
* 

i = -4
while i <= 4:
    j = 0
    while j <=4-abs(i):
        print("*",end = " ")
        j += 1
    print("")
    i += 1