Question

I have written code to display a temp reading on a RPI to an LCD screen in python. I am required to have the data be sent to a JSON file and am having trouble modifying this to happen. I know I import JSON but then do I create a data set or can I pull it directly from the data that is being collected. Below is my code.

from grovepi import *
from grove_rgb_lcd import *
from time import sleep
from math import isnan

dht_sensor_port = 7 # connect the DHt sensor to port 7
dht_sensor_type = 0 # use 0 for the blue-colored sensor and 1 for the white-colored sensor

# set green as backlight color
# we need to do it just once
# setting the backlight color once reduces the amount of data transfer over the I2C line
setRGB(0,255,0)

while True:
try:
# get the temperature and Humidity from the DHT sensor
[ temp,hum ] = dht(dht_sensor_port,dht_sensor_type)

# change temp reading from celsius to fahrenheit
temp = ((temp/5.0)*9)+32

# round the temp to 2 decimal places so it will read on the LCD screen
new_temp = round(temp, 2)

print("temp =", temp , "F\thumidity =", hum,"%")

# check if we have nans
# if so, then raise a type error exception
if isnan(new_temp) is True or isnan(hum) is True:
raise TypeError('nan error')

t = str(new_temp)
h = str(hum)

# instead of inserting a bunch of whitespace, we can just insert a \n
# we're ensuring that if we get some strange strings on one line, the 2nd one won't be affected
setText_norefresh("Temp:" + t + "F\n" + "Humidity :" + h + "%")

except (IOError, TypeError) as e:
print(str(e))
# and since we got a type error
# then reset the LCD's text
setText("")

except KeyboardInterrupt as e:
print(str(e))
# since we're exiting the program
# it's better to leave the LCD with a blank text
setText("")
break

#

Answer 1

I guess from your code that you want to dump the temp and humidity to your json file.

first of all import json at top of your code.

import json

Now for dumping into json file you need to open a jason file in write mode:

with open('temp_hum.json','w') as my_json:

here you need to dump the temp and humidity data using:

json.dump(temp_hum_details,my_json)

So before this you need to create the dataset fro temp_hum_details as:

temp_hum_details= {

'temp' : temp,

'humidity' : hum

}

So for each iteration or reading from the RPI, if you do this, the data will be dumped into the json file. Hope it helps.

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