python 语法

1.python self代表类的实例，在刷leetcode的时候可以当成全局变量使用

 2.pass by reference/pass by value

         pass by reference: mutable objects

                 array,dict, set, deque, heapq, treenode

         pass by value: immutable

                integer,string,tuple

3.sort

        simple ascending sort:

                sorted([5, 2, 3, 1, 4])

        list.sort() method. It modifies the list in-place 

        lambda sort:

        student_tuples = [
        ...     ('john', 'A', 15),
        ...     ('jane', 'B', 12),
        ...     ('dave', 'B', 10),
        ... ]
        >>> sorted(student_tuples, key=lambda student: student[2])   # sort by age
        [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]