python 函数参数传递

Python’s pass-by-assignment scheme isn’t quite the same as C++’s reference parameters
option, but it turns out to be very similar to the C language’s argument-passing
model in practice:
• Immutable arguments are effectively passed “by value.” Objects such as integers
and strings are passed by object reference instead of by copying, but because
you can’t change immutable objects in-place anyhow, the effect is much like making
a copy.
• Mutable arguments are effectively passed “by pointer.” Objects such as lists
and dictionaries are also passed by object reference, which is similar to the way C
passes arrays as pointers—mutable objects can be changed in-place in the function,
much like C arrays.
Of course, if you’ve never used C, Python’s argument-passing mode will seem simpler
still—it involves just the assignment of objects to names, and it works the same whether

the objects are mutable or not.

python函数参数是值传送还是引用传送只取决于传送的这个对象是可变的，还是不可变的，

如果是可变的，就是引用参数传递，否则就是值传递。

可变对象：如list、map、自定义的object；

不可变对象：如numeric、string；