您需要在每次查询之后提交连接。这将提交当前事务，并确保下一个（隐式）事务将获取上一个事务处于活动状态时所做的更改。

# Main loop

while True:

    # SQL query
    sql = "SELECT * FROM table"

    # Read the database, store as a dictionary
    mycursor = mydb.cursor(dictionary=True)
    mycursor.execute(sql)

    # Store data in rows
    myresult = mycursor.fetchall()

    # Transfer data into list
    for row in myresult:
        myList[int(row["rowID"])] = (row["a"], row["b"], row["c"])

        print(myList[int(row["rowID"])])

    # Commit !
    mydb.commit()
    print("---")
    sleep (0.1)

这里的概念是隔离级别。从文件（我的）：
可重复读取
这是innodb的默认隔离级别。同一事务中的一致读取读取第一次读取所建立的快照。

我会做一些改变。首先，在while循环之前声明游标。我也会做一个缓冲游标。最后，在文件完成后关闭游标和db。希望这有帮助。

import mysql.connector
from mysql.connector import Error
from time import sleep

# Create empty list to store values from database.

listSize = 100
myList = []

for i in range(listSize):
    myList.append([[0,0,0]])

# Connect to MySQL Server

mydb = mysql.connector.connect(host='localhost',
                               database='db',
                               user='user',
                               password='pass')
mycursor = mydb.cursor(buffered=True, dictionary=True)

# Main loop

while True:

    # SQL query
    sql = "SELECT * FROM table"

    # Read the database, store as a dictionary
    mycursor.execute(sql)

    # Store data in rows
    myresult = mycursor.fetchall()

    # Transfer data into list
    for row in myresult:
        myList[int(row["rowID"])] = (row["a"], row["b"], row["c"])

        print(myList[int(row["rowID"])])

    print("---")
    sleep (0.1)
mycursor.close()
mydb.close()