面试题01-有价值
title: 面试题01-有价值
date: 2018-10-25 21:11:39
tags: 面试题-某里
希望那出题狗?能看到，面试题没必要这么HY coder吧
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题目：
```sql CREATE TABLE `student` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(250) DEFAULT '1' COMMENT '名字', `teacher_id` int(11) DEFAULT '0' COMMENT '老师id' ) ENGINE=InnoDB CHARSET=utf8 COMMENT='学生表'; CREATE TABLE `teacher` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(250) DEFAULT '1' COMMENT '名字', `check_time` datetime NOT NULL COMMENT '打卡时间' ) ENGINE=InnoDB CHARSET=utf8 COMMENT='老师表' ``` 用python语言, 写一个"老师"进程, 要求: 1. 进程启动时, 会往teacher表里面插入一条记录, 记下这条记录的id值, 保存为t_id. 2. 进程定期更新其t_id对应记录的"check_time"字段. 3. 进程定期扫描student表, 如果有teacher_id为0的记录, 将该字段更新为其t_id. 4. 当启动两个进程A和B时, 这两个进程可以平分所有的student, 即一半student的teacher_id为进程A的t_id, 另一半student的teacher_id为进程B的t_id. 5. 再启动一个进程C的时候, 1/3的student的teacher_id为进程A的t_id, 1/3为归进程B, 1/3归进程C. 6. 当进程A因为各种原因挂了, 不再更新check_time字段时, 进程B和进程C可以瓜分进程A托管的学生. -
我写的答案：
import multiprocessing from pymysql import * import datetime import threading import time import os class MyMysql(object): """ 进程类 """ def __init__(self): self.row_range = "" # 扫面的工作范围元组类型 self.con = connect( host='localhost', port=3306, database='ceshi', user='root', password='mysql', charset='utf8') self.cs = self.con.cursor() self.time = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S") self.t_id = "" self.q = "" # todo 这里留一个通讯队列 self.q1 = "" # 线程运行数量队列 def mysql_init(self): """ # 1. 进程启动时, 会往teacher表里面插入一条记录, 记下这条记录的id值, 保存为t_id. :return: 返回值是t_id """ self.cs.execute("""insert into teacher(check_time) \ values(str_to_date(\'%s\','%%Y-%%m-%%d %%H:%%i:%%s'));""" % self.time) self.cs.execute("""SELECT LAST_INSERT_ID()""") self.t_id = self.cs.fetchone()[0] def update_teacher(self): """ # 2. 进程定期更新其t_id对应记录的"check_time"字段. --实现 :return: """ while True: print("update ok") time.sleep(3) self.time = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S") self.cs.execute("""update teacher set \ check_time=str_to_date(\'%s\','%%Y-%%m-%%d %%H:%%i:%%s') where id=%d;""" % (self.time, self.t_id)) self.con.commit() def up_stu_tid(self): """ # 3. 进程定期扫描student表, 如果有teacher_id为0的记录, 将该字段更新为其t_id. # 4. 当启动两个进程A和B时, 这两个进程可以平分所有的student, 即一半student的teacher_id为进程A的t_id, # 另一半student的teacher_id为进程B的t_id。 # 5. 再启动一个进程C的时候, 1/3的student的teacher_id为进程A的t_id, 1/3为归进程B, 1/3归进程C. :return: """ while True: time.sleep(5) self.cs.execute( """select id from student where teacher_id=0 limit %d,%d;""" % self.row_range) a = self.cs.fetchall() for i in a: self.cs.execute( """update student set teacher_id=%s where id= %s""" % (self.t_id, i[0])) def tell_mian_live(self): """ 告诉主进程我还活着 和 进程 id 此函数要定期执行 :return: """ time.sleep(1) # 每两秒执行一次，进行函数的使用 self.q.put(os.getpid()) # 将子进程号放到队列中 def get_p_live(self): """ 更改全局变量 :return: """ while True: try: self.row_range = self.q1.get() except Exception as e: print(e) def my_pro_run(self, range_r, q, q1): """ 总的运行程序 :return: """ self.q = q # 重置进程队列 self.q1 = q1 self.row_range = range_r print(self.row_range) self.mysql_init() print(self.t_id, type(self.t_id)) # todo 开启定时报告存活 功能 threading.Thread(target=self.tell_mian_live).start() threading.Thread(target=self.update_teacher).start() threading.Thread(target=self.up_stu_tid).start() self.con.commit() class JinCheng(object): def __init__(self, fun, num): self.conn = connect( host='localhost', port=3306, database='ceshi', user='root', password='mysql', charset='utf8') self.cs2 = self.conn.cursor() self.cs2.execute("select count(*) from teacher;") self.mysql_row = self.cs2.fetchall()[0][0] # 数据中的行数 self.pro_list = [fun] * num self.pro_arg = "" self.q = multiprocessing.Queue() # todo 进程通讯工具 self.q1 = multiprocessing.Queue() # todo 进程通讯工具 self.chang_num_pro = 0 def start_pro(self): for i in self.pro_list: time.sleep(0.02) # 延迟0.02 秒 生成文件 multiprocessing.Process(target=i, args=( (self.pro_arg[0][len(self.pro_list) - 1], self.pro_arg[1]), self.q, self.q1) ).start() print(" 开启成功") def cha_xu(self, a, b): """ :param a: 数据库行数 :param b: 进程数 :return: 步进值和点值 -》 第几个进程 号-1 加步长 """ step_int = a // len(self.pro_list) if step_int % 2 == 0: step = round(a / b) + 1 else: step = round(a / b) limit_page = [] for i in range(0, a, step): limit_page.append(i) self.pro_arg = (limit_page, step) print(self.pro_arg) def check_pro(self): """ 判断开启的进程和进程列表中的数量是不是相同 此函数单独开工线程使用 :return: """ start_pro = len(self.pro_list) print("start_pro", start_pro) def q_getpid(start_pro): get_q = [] # 进程号列表 for i in range(start_pro): try: count = self.q.get() if count in get_q: pass else: get_q.append(count) except Exception as e: print(e) return get_q while True: a = q_getpid(start_pro) b = q_getpid(start_pro) if a == b: pass else: for i in a: if i in b: pass else: print("死掉的进程", i) start_pro -= 1 # 进程数减少1 self.chang_num_pro = start_pro self.cha_xu(self.mysql_row, self.chang_num_pro) self.q1.put(self.pro_arg) # 将更改后的参数发送给子进程 def run_pro(self): """ 运行初始化 :return: """ self.cha_xu(self.mysql_row, len(self.pro_list)) self.start_pro() threading.Thread(target=self.check_pro).start() if __name__ == '__main__': a = MyMysql() jin = JinCheng(a.my_pro_run, 3) jin.run_pro() -
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