17-Generator

Yield

• 用yield代替return，可以返回多次
• 返回值是一个iterator

#yield from
for x in a:
    yield a
# 等价于
yield from a

• 获得一个单词中的所有字串

def prefixes(s):
    if s:
    yield from prefixer(s[:-1])
    yield s

def substrings(s):
    if s:
        yield from prefisxes(s)
        yield from substrings(s[1:])

Example: partitions

def partitions(n, m):
    if n>0 and m>0:
        if n==m:
            yield str(m)
        for p in partiotions(n-m, m):
            yield p+'+'+str(m)
        yield from partitions(n, m-1)

18/19-Object/Attribute

Class

calss <name>:
    name = XXX
    def dance():
        return XXX
    ...
    <suite> #attributes

• 使用__init__初始化class
• self: A new instance of the class in create #相当于一张等待书写的白纸

class Account:
    def __init__(self, account_holder): #Constructor
        self.balance = 0 
        self.holder = account_holder

Attribute

• 类中的attribute值改变，所有实例的值跟着改变
• class中为function，instance中为method

Ant

• 以类造类
• 将父类属性和函数传递给子类（用下面的函数继承）

class FireAnt(Ant):
or
class LongThrower(ThrowerAnt)

• 父类继承 (继承父类属性，或将变量传递给父类构造函数)
• super() 用于多重继承，当有多个继承出现时使用

class Chidren(Partents):
    def __init__ (self, value):
        super.__init__(value)