Python从数据库取数，对时间进行处理，统计数据汇总后画图

#-*- coding: utf8 -*-
import odbc
import numpy as np
import pylab as pl
allDate = []
allData = []
if __name__ == '__main__':
print("run success")
allDate, allData  =  odbc.getData()
# print(allDate)
pl.plot(allDate,allData)
pl.show()
else:
print("run error")import pymysql as mysql
import time, datetime
mysql.install_as_MySQLdb()
def getData():
try:
# 获取一个数据库连接，注意如果是UTF-8类型的，需要制定数据库
conn = mysql.connect(host='xxx.xxx.xxx.xxx', user='xxx', passwd='xxx', db='xxx', port=xxx,
charset='utf8')
cur = conn.cursor()  # 获取一个游标
sql = """SELECT a.changenum,a.updatetime
from xxxx a join xxxxx b
on a.x = b.x
where b.name = 'xxx'
and a.updatetime > '2017-07-01 00:00:00'
ORDER BY updatetime ASC"""
cur.execute(sql)  # 游标执行sql查询语句
data = cur.fetchall()  # fetchall()则是接收全部的返回结果行
change_data = []
change_date = []
for d in data:  # 循环结果进行显示
change_data.append(d[0])
change_date.append(d[1])
cur.close()  # 关闭游标
conn.close()  # 关闭连接
except Exception:
print("查询失败")
print(change_data)
print(change_date)

first_date = datetime.datetime.strptime(
datetime.datetime.strftime(change_date[0], '%Y-%m-%d %H:%M:%S')[0:10] + " 00:00:00", '%Y-%m-%d %H:%M:%S')
# 获取第一个时间数据，取得日期部分，向前
last_date = datetime.datetime.strptime(
datetime.datetime.strftime(change_date[len(change_date) - 1], '%Y-%m-%d %H:%M:%S')[0:10] + " 00:00:00",
'%Y-%m-%d %H:%M:%S') + datetime.timedelta(days=1)
# 获取最后一个时间数据，取得日期部分，向后
# print(first_date)
# print(last_date)
date = []
data = []
temp_date = first_date
n = 0
num = 0
#外层循环，每次增加半小时
while temp_date < last_date:
for i in range(n, len(change_date)):
#内层循环，循环数据库数据，在该半小时之内的变换情况
if temp_date <= change_date[i] < temp_date + datetime.timedelta(minutes=30):
num += change_data[i]
else:
break
data.append(num)  # 对变化情况进行记录以便于后续画图的Y轴数据
num = 0
n = i
temp_date = temp_date + datetime.timedelta(minutes=30)  # 横轴时间数据
date.append(temp_date)

print(len(date))
print(len(data))
print(date)
print(data)
return  date, data  # 因为未对齐到外层的getData()主函数，曾经导致出错