a = [['hello world','','']]
b = a[0]
print b
b[0] = b[0] + '123'
a.append(b)
print a
b = a[0]
print b
b[0] = b[0] + '123'
a.append(b)
print a
以上属于引用传递,打印输出为[['hello world123','',''],['hello world123','','']]
如果想不改变a的值,解决办法是将a[0]深拷贝一份后再操作
更详细说明见: https://www.cnblogs.com/loleina/p/5276918.html