求大神帮忙用python写一个杨辉三角的程序

def gettriangle(num):
    triangle=[]
    for i in range(0,num+1):
        tmp=[1]*(i+1)
        for j in range(1,i):
            tmp[j]=triangle[i-1][j-1]+triangle[i-1][j]
        triangle.append(tmp)
    return triangle
def printtriangle(triangle,width=4):
    column=len(triangle[-1])*width;
    for sublist in triangle:
        result=[]
        for element in sublist:
            tmp='{0:^{1}d}'.format(element,width)
            result.append(tmp)
        print('{0:^{1}s}'.format(''.join(result),column))
if __name__=='__main__':
    num=int(input("Enter a nonnegative integer:"))
    triangle=gettriangle(num)
    printtriangle(triangle,4)