题中的y= [19,17,15,19,15,11,7,3,,13,11,9,7,5,3,1]

y= [19,17,15,19,15,11,7,3,13,11,9,7,5,3,1]
g = list('abcdefg')
y[1::2] = g
print(y)

y= [19,17,15,19,15,11,7,3,,13,11,9,7,5,3,1]
a='a'
for i in range(1,len(y)+1,2):
    y[i]=a
    a=chr(ord(a)+1)