write continuous data to csv file

Question

I am using a code in python to get the data of a sensor, the sensor measures vibration in different axis. the code works well but i am trying to write the output data to a csv file automatically.

this is the code i am using:

import smbus            
from time import sleep          

#some MPU6050 Registers and their Address
PWR_MGMT_1   = 0x6B
SMPLRT_DIV   = 0x19
CONFIG       = 0x1A
GYRO_CONFIG  = 0x1B
INT_ENABLE   = 0x38
ACCEL_XOUT_H = 0x3B
ACCEL_YOUT_H = 0x3D
ACCEL_ZOUT_H = 0x3F
GYRO_XOUT_H  = 0x43
GYRO_YOUT_H  = 0x45
GYRO_ZOUT_H  = 0x47


def MPU_Init():
    #write to sample rate register
    bus.write_byte_data(Device_Address, SMPLRT_DIV, 7)

    #Write to power management register
    bus.write_byte_data(Device_Address, PWR_MGMT_1, 1)

    #Write to Configuration register
    bus.write_byte_data(Device_Address, CONFIG, 0)

    #Write to Gyro configuration register
    bus.write_byte_data(Device_Address, GYRO_CONFIG, 24)

    #Write to interrupt enable register
    bus.write_byte_data(Device_Address, INT_ENABLE, 1)

def read_raw_data(addr):
    #Accelero and Gyro value are 16-bit
        high = bus.read_byte_data(Device_Address, addr)
        low = bus.read_byte_data(Device_Address, addr+1)

        #concatenate higher and lower value
        value = ((high << 8) | low)

        #to get signed value from mpu6050
        if(value > 32768):
                value = value - 65536
        return value


bus = smbus.SMBus(1)    # or bus = smbus.SMBus(0) for older version boards
Device_Address = 0x68   # MPU6050 device address

MPU_Init()

print (" Reading Data of Gyroscope and Accelerometer")

while True:

    #Read Accelerometer raw value
    acc_x = read_raw_data(ACCEL_XOUT_H)
    acc_y = read_raw_data(ACCEL_YOUT_H)
    acc_z = read_raw_data(ACCEL_ZOUT_H)

    #Read Gyroscope raw value
    gyro_x = read_raw_data(GYRO_XOUT_H)
    gyro_y = read_raw_data(GYRO_YOUT_H)
    gyro_z = read_raw_data(GYRO_ZOUT_H)

    #Full scale range +/- 250 degree/C as per sensitivity scale factor
    Ax = acc_x/16384.0
    Ay = acc_y/16384.0
    Az = acc_z/16384.0

    Gx = gyro_x/131.0
    Gy = gyro_y/131.0
    Gz = gyro_z/131.0


    print ("Gx=%.2f" %Gx, u'\u00b0'+ "/s", "\tGy=%.2f" %Gy, u'\u00b0'+ "/s", "\tGz=%.2f" %Gz, u'\u00b0'+ "/s", "\tAx=%.2f g" %Ax, "\tAy=%.2f g" %Ay, "\tAz=%.2f g" %Az)     
    sleep(2)

'''''

now the writing order i tried to use looks like this:

finaldata = { "Gx=%.2f" %Gx, u'\u00b0'+ "/s", "\tGy=%.2f" %Gy, u'\u00b0'+ "/s", "\tGz=%.2f" %Gz, u'\u00b0'+ "/s", "\tAx=%.2f g" %Ax, "\tAy=%.2f g" %Ay, "\tAz=%.2f g" %Az }
with open("accell.csv", "a")as output:
        writer = csv.writer(output, delimiter=",", lineterminiator = '\n')
        writer.writerow(finaldata)
sleep(2)

'''''''

but this writing to csv code is not working , can i know why please?

Answer 1

first, add import csv to your code , then use this part to write in csv file :

import smbus            
from time import sleep       
import csv

#some MPU6050 Registers and their Address
PWR_MGMT_1   = 0x6B
SMPLRT_DIV   = 0x19
CONFIG       = 0x1A
GYRO_CONFIG  = 0x1B
INT_ENABLE   = 0x38
ACCEL_XOUT_H = 0x3B
ACCEL_YOUT_H = 0x3D
ACCEL_ZOUT_H = 0x3F
GYRO_XOUT_H  = 0x43
GYRO_YOUT_H  = 0x45
GYRO_ZOUT_H  = 0x47


def MPU_Init():
    #write to sample rate register
    bus.write_byte_data(Device_Address, SMPLRT_DIV, 7)

    #Write to power management register
    bus.write_byte_data(Device_Address, PWR_MGMT_1, 1)

    #Write to Configuration register
    bus.write_byte_data(Device_Address, CONFIG, 0)

    #Write to Gyro configuration register
    bus.write_byte_data(Device_Address, GYRO_CONFIG, 24)

    #Write to interrupt enable register
    bus.write_byte_data(Device_Address, INT_ENABLE, 1)

def read_raw_data(addr):
    #Accelero and Gyro value are 16-bit
        high = bus.read_byte_data(Device_Address, addr)
        low = bus.read_byte_data(Device_Address, addr+1)

        #concatenate higher and lower value
        value = ((high << 8) | low)

        #to get signed value from mpu6050
        if(value > 32768):
                value = value - 65536
        return value


bus = smbus.SMBus(1)    # or bus = smbus.SMBus(0) for older version boards
Device_Address = 0x68   # MPU6050 device address

MPU_Init()

print (" Reading Data of Gyroscope and Accelerometer")

while True:

    #Read Accelerometer raw value
    acc_x = read_raw_data(ACCEL_XOUT_H)
    acc_y = read_raw_data(ACCEL_YOUT_H)
    acc_z = read_raw_data(ACCEL_ZOUT_H)

    #Read Gyroscope raw value
    gyro_x = read_raw_data(GYRO_XOUT_H)
    gyro_y = read_raw_data(GYRO_YOUT_H)
    gyro_z = read_raw_data(GYRO_ZOUT_H)

    #Full scale range +/- 250 degree/C as per sensitivity scale factor
    Ax = acc_x/16384.0
    Ay = acc_y/16384.0
    Az = acc_z/16384.0

    Gx = gyro_x/131.0
    Gy = gyro_y/131.0
    Gz = gyro_z/131.0


    print ("Gx=%.2f" %Gx, u'\u00b0'+ "/s", "\tGy=%.2f" %Gy, u'\u00b0'+ "/s", "\tGz=%.2f" %Gz, u'\u00b0'+ "/s", "\tAx=%.2f g" %Ax, "\tAy=%.2f g" %Ay, "\tAz=%.2f g" %Az)

    finaldata = {"Gx=%.2f" % Gx, u'\u00b0' + "/s", "\tGy=%.2f" % Gy, u'\u00b0' + "/s", "\tGz=%.2f" % Gz,
                 u'\u00b0' + "/s", "\tAx=%.2f g" % Ax, "\tAy=%.2f g" % Ay, "\tAz=%.2f g" % Az}
    with open("\\test.csv", "a")as output:
        writer = csv.writer(output, delimiter=",")
        writer.writerow(finaldata)

    sleep(2)

Answer 2

@nimajv is on the right track, but I think you forgot to open the file in a+ mode.

a+: Opens a file for both appending and reading. The file pointer is at the end of the file if the file exists. The file opens in the append mode. If the file does not exist, it creates a new file for reading and writing - Python Files IO

This is the case when you haven't created the file of course. If you did, then you should replace the part of his code with the true file path. Additionally, you also should replace his dummy path - \\test.csv with whatever true path you want. If you simply go with test.csv it will create the file in the same directory (with the a+ mode of course) where you've ran the script from.