无法使用Python在表中插入或在MySQL中创建表

Question

I have a arduino uno and temp36. I read the sensor value from the arduino serial Monitor with Python. It works!!

But I can't insert in a created MySQL Table using Python and I don't know why. I have no error or warning.

import serial
import time
import MySQLdb

dbhost = 'localhost'
dbname = 'test'
dbuser = 'X'
dbpass = 'Y'
ser = serial.Serial('COM7',9600,timeout=1) # On Ubuntu systems, /dev/ttyACM0 is the default path to the serial device on Arduinos, yours is likely different.
while 1:
time.sleep(1)
the_goods = ser.readline()
str_parts = the_goods.split(' ')
conn = MySQLdb.connect (host = dbhost,
                user = dbuser,
                passwd = dbpass,
                db = dbname)
cursor = conn.cursor ()
sql = "INSERT INTO arduino_temp (temperature) VALUES ('%s');" % (str_parts[0])
print "Number of rows inserted: %d" % cursor.rowcount
try:
    cursor.execute(sql)
except:
    pass
cursor.close ()
conn.autocommit=True
conn.close ()
print the_goods

Am I doing something wrong?

Those Value in SQL-table need to be plot in php (real time ploting)

Hardware: windows 7, Python 2.7, Python editor:Pyscripter, arduino uno, MySQL Workbench

Answer 1

You have to commit after executing the sql statement:

cursor.execute(sql)
cursor.commit()

or set autocommit=True after the connection is established.

Answer 2

If you open database connection it is initially with autocommit=False mode, so after you execute SQL statement you must commit() it. Also do not pass on exception. This way you will not see problems. You can log exception into file. You also use cursor.rowcount before you execute INSERT statement. Use it after it.

From your comments it seems that you do not defined arduino_temp database. I do not have MySQL database but I have tested such code with PostgreSQL and ODBC driver. You can use it to test your database and driver:

import MySQLdb
import traceback


def ensure_table(conn):
    cursor = conn.cursor()
    try:
        cursor.execute('SELECT COUNT(*) FROM arduino_temp')
        for txt in cursor.fetchall():
            print('Number of already inserted temepratures: %s' % (txt[0]))
    except:
        s = traceback.format_exc()
        print('Problem while counting records:\n%s\n' % (s))
        print('Creating arduino_temp table ...')
        # table arduino_temp does not exist
        # you have to define table there
        # you will probably have to add some columns as:
        #  test_id SERIAL primary key,
        #  test_date timestamp default CURRENT_TIMESTAMP,
        # and add index on test_date
        cursor.execute('CREATE TABLE arduino_temp (temperature integer)')
        print('table created')
    cursor.close()


def insert_temperature(conn, temperature):
    cursor = conn.cursor()
    #cursor.execute("INSERT INTO arduino_temp (temperature) VALUES (?)", (temperature, ))
    #cursor.execute("INSERT INTO arduino_temp (temperature) VALUES (%s)", (temperature, ))
    cursor.execute("INSERT INTO arduino_temp (temperature) VALUES (%d)" % (int(temperature)))
    print("Number of rows inserted: %d" % (cursor.rowcount))
    conn.commit()
    cursor.close()


def main():
    # ...
    conn = MySQLdb.connect (host = dbhost, user = dbuser, passwd = dbpass, db = dbname)
    #conn = pyodbc.connect('DSN=isof_test;uid=dbuser;pwd=dbpass')
    ensure_table(conn)
    insert_temperature(conn, 10)


main()

If you have problem with database create test code and use small functions. Your code is mixed reading temperature from serial interface and inserting it into database. Make separate functions for each operation.