python回测与交易框架之坑爹的类与类之间变量的传输

python类之间变量的传输的时候变量是字符串和变量是列表或者字典是完全不同的：

试着把self.time的格式分别用字符串，列表，和字典，看输出的结果：

import time 
class Book:
    def __init__(self):
        self.time=[None]
    def update_time(self):
        self.time[0]=time.strftime("%Y-%m-%d %H:%M:%S", time.localtime())
class Strategy:
    def __init__(self,book):
        self.time=book.time
book=Book()
strategy=Strategy(book)     
for i in range(10):
    time.sleep(1)
    book.update_time()
    print( strategy.time)

self.time是字符串的形式：

None

None

None

None

None

None

None

None

None

None

self.time是列表的形式：

['2018-11-21 19:49:04']

['2018-11-21 19:49:05']

['2018-11-21 19:49:06']

['2018-11-21 19:49:07']

['2018-11-21 19:49:08']

['2018-11-21 19:49:09']

['2018-11-21 19:49:10']

['2018-11-21 19:49:11']

['2018-11-21 19:49:12']

['2018-11-21 19:49:13']

self.time是字典形式的：

{'datetime': '2018-11-21 19:51:40'}

{'datetime': '2018-11-21 19:51:41'}

{'datetime': '2018-11-21 19:51:42'}

{'datetime': '2018-11-21 19:51:43'}

{'datetime': '2018-11-21 19:51:44'}

{'datetime': '2018-11-21 19:51:45'}

{'datetime': '2018-11-21 19:51:46'}

{'datetime': '2018-11-21 19:51:47'}

{'datetime': '2018-11-21 19:51:48'}

{'datetime': '2018-11-21 19:51:49'}