Python函数得到了2个列表，但只更改了1个

Question

为什么Lista1会被更改，而Lista2不会？哪些方法直接改变列表

def altera(L1, L2):
    for elemento in L2:
        L1.append(elemento)
    L2 = L2 + [4]
    L1[1]= 10
    del L2[0]
    return L2[:]

Lista1 = [1, 2, 3]
Lista2 = [1, 2, 3]

Lista3 = altera(Lista1, Lista2)

print(Lista1)
print(Lista2)
print(Lista3)

Answer 1

L2 = L2 + [4]此语句创建新变量

如果将此语句更改为L2.extend([4])或L2 += [4]，则它将更改L2的值，即[2, 3, 4]

在赋值前后打印id的L2

>>> L2 = [1,2,3]
>>> id(L2)
3072769420L    # ID of L2 
>>> L2 += [4]
>>> id(L2)
3072769420L    # Same ID of L2
>>> L2
[1, 2, 3, 4]
>>> L2 = L2+[5]
>>> id(L2)
142773548      # New variable which name  is L2