py 一些built-in函数

python语言自带的内置函数.
碰到陌生的函数, 可以使用help(function_name)来参考.

• getattr(obj, name)
  是否拥有某字段

• sorted(iterable, key=None, reverse=False)
  返回排序后的list, 不会改变参数中元素的顺序.

a_dict = {1:100,2:300,3:200,4:100}#按照value的值倒序排序result = sorted(a_dict.items(), key=lambda t:(t[1],t[0]), reverse=True) print(result)   #[(2, 300), (3, 200), (4, 100), (1, 100)]

• id(obj)
  返回对象的内存地址.
  Return the identity of an object.
  This is guaranteed to be unique among simultaneously existing objects.
  (CPython uses the object’s memory address.)