object and namespace

http://effbot.org/zone/python-objects.htm

几点总结：

(1) 类的基本属性

. id, returned by id(obj)

. type, returned by type(obj)

. some content

. methods; some objects have methods to change the content, and some don’t; eg, list vs. turple

. names

(2) namespace

. namespace are pairs of (name, object reference). eg., n=10 where ‘n’ is the name and ‘10’ is the int object.

. names are not really properties of objects

(3) assignment

举例说明。

name = 10

name = 20

. add name ‘name’ to local namespace, and refer it to an integer object containing value 10

. refer name to another integer object containing value 20

. the original object ‘10’ is not affected by this operation and it doesn’t care

再举一个object可变的例子。

name = []

name.append(a)

. add name ‘name’ to a local namespace, and refer it to an empty list object; this modifies the namespace

. an object method is called; this modifies the content of the the list object, but it doesn’t touch the namespace

(4) note

Things like name.attr and name[index] are just syntactic sugar for method calls.

The first corresponds to __setattr__/__getattr__, the second to __setitem__/__getitem__ (depending on which side of the assignment they appear).

--> syntactic suger是指为了更容易阅读而设计出来的编程语言的语法