#letters中的元素数量不一定，但肯定是3的倍数

newletter = ["a", "b", "c", "d", "e", "f", "g", "h", "i",]

#想要的结果是每三个元素为一行

print(newletter[0],newletter[1],newletter[2])
print(newletter[3],newletter[4],newletter[5])
print(newletter[6],newletter[7],newletter[8])

a b c
d e f
g h i
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