Retrieving values from mysql database and saving them to an empty array with python-CodePudding

I have a MySQL DB (using MySQL workbench) having two tables (ecg_pat_tbl & ecg_data_tbl), and sending float values, Date and Time to columns voltage, date, and time respectively, and am also plotting a graph at the same time (voltage against time), everything is going well, now I want to retrieve both voltage and time values save them to different arrays so that I can use them for analysis, how do I go about retrieving and saving them? The code below is the function am using to plot and save to the DB.

data =[]
_condition = False
amount = 0

def graphing():
    global _condition, data
    if (_condition == True):
        try:
            identity = identity_var.get() # Getting patient ID
            date_time=datetime.datetime.now()
            my_time='{}:{}:{}'.format(date_time.hour,date_time.minute,date_time.second)
            my_date='{}/{}/{}'.format(date_time.year, date_time.month,date_time.day)
            
            serial_data = _serial.readline()
            serial_data.decode()
            
            float_data = float(serial_data[0:4])
            query = "INSERT INTO ecg_data_tbl(patient_id, voltage, date, time) VALUES(%s, %s, %s, %s)"
            mycursor.execute(query, (identity, float_data, my_date,  my_time))
            mycursor.execute("commit")
            
            data.append(float_data)
            ax.plot(data, color="blue")
            canvas.draw_idle()
    
        except ValueError as e:
            _condition = False
            start_button['state'] = NORMAL
            freeze_button['state'] = DISABLED
            save_button['state'] = DISABLED
            insert_button['state'] = DISABLED
            messagebox.showinfo("Connection", "Check connnection of the patient cable")

all responses are appreciated.

CodePudding user response：

Correct me if I'm wrong, but it seems your only issue is unzipping the values from the format cursor's return value: (time_0, volt_0), (time_1, volt_1), .... The code should look something like this.


query = "SELECT time, voltage FROM ecg_data_tbl WHERE patient_id=?"
result = cursor.execute(query, (identity,)).fetchall()
# (time_0, volt_0), (time_1, volt_1), ...
times, volts = list(zip(*result))
# (time_0, time_1, ...), (volt_0, volt_1, ...)