python inside pass an object reference is equivalent to transfer address
id () function returns the object at the memory address
a = test showed a shallow copy, a and a test point to the same memory address or
b = test [:] is a deep copy, the equivalent of a copy of the memory address, again with this new variable b to point to the memory address
One problem is shallow copy will happen
Shallow Copy: Copy before, after a copy with the same memory address, once the value is modified, all variants will follow
By a modification of the value, test also become. Can copy.copy or copy.deepcopy.
Both the efficiency is not the same, which is recursive, the speed slower than copy.copy
Immutable objects: int str float tuple, mutable objects: dict set list
Immutable objects: the value of the object is stored in the address will not be changed (so-called change is the creation of a new address and the value of the new object in the new address in the original object has not changed); mutable objects : objects stored in the address value will change in situ
Immutable objects str
Variable object list, change the value in place, the same memory address
