Recording Temperature and Humidity Data to a Memory Stick

Question

I have a Adafruit DHT22 sensor connected to my Raspberry Pi B+. I want to put this in an outbuilding to monitor the temperature and humidity over a period of time. The building has mains power but no wifi or cable network. I propose to have the data saved on a memory stick in a csv file.

As a base for the script I am using the simpletest.py script which I downloaded from Adafruit. The script works proving there is nothing wrong with the hardware. I have a copy of the Raspberry Cookbook and have downloaded the temperature sensor data to memory stick script from that publication. I am attempting to combine them to get what I want.

#!/usr/bin/python

# imports to pick up the dependencies to make this work

import glob, datetime, os, time

# defines the period between data samples.  For the purpose of test this is set low.  The actual
# time will be some minutes between samples
log_period = 10 # seconds

# Add the data logging stuff below here

# logging_folder = glob.glob('/media/KINGSTON/Raspberry_Data/')[0]
logging_folder = glob.glob('/home/pi/*')[0]
dt = datetime.datetime.now()
file_name = "temp_log_{:%Y_%m_%d}.csv".format(dt)
logging_file = logging_folder + '/' + file_name


# Add the data logging stuff above here

import Adafruit_DHT


sensor = Adafruit_DHT.DHT22




pin = 4


# The two pieces of data I want are temperature and humidity.  I just need to open the file
# and put them in.


#def log_temp():  # Don't believe I need a temp???
#    temp_c, temp_f = read_temp() # Data names from old program
dt = datetime.datetime.now()
f = open(logging_file, 'a') # Open the logging file with the intention of amending it
#f.write('\n"{:%H:%M:%S}",'.format(dt) #Origin line removed as it caused a syntax error
f = write('\n"{:%H:%M:%S}",'.format(dt) # Create a new line and insert HMS
>>>f.write(str(temperature)) # Write the string temperature Throws up syntax error
# with carat under 'f'.
#f = write(str(temperature))
f.close()

print("Logging to: " + logging_file)
while True:
    log_temp()
    time.sleep(log_period)

The above works fine until it gets to the line with >>> this does not appear in the script but is only used to highlight the problem. Also, I have not directed the output to /media/ yet just to /pi/ as this is still being debugged.

I had hoped it was just a simple case of directing the two data sets (temperature and humidity) to the logging file but I seem to have lost my way.

Can anyone offer any help please?

Regards,

Harry

Answer 1

You are missing closing bracket one line above

f = write('\n"{:%H:%M:%S}",'.format(dt)

it should be:

f = write('\n"{:%H:%M:%S}",'.format(dt)) #<-one more bracket

Answer 2

f.write(str(temperature)) Throws up syntax error

Probably because no variable named temperature exists in that script.

---

In a comment below you've said you accidentally left some lines out including this:

if humidity is not None and temperature is not None:
    print 'Temp={0:0.1f}@C Humidity={1:0.1f}%'.format(temperature, humidity)
else: print 'Failed to get reading. Try again!' 

And that you believe "this is where the variables Temperature and Humidity are defined". You have essentially no programming experience. That's fine -- I understand you are just trying to use the script to accomplish something.

Unfortunately, working with code is not always as straightforward as one may think it is going to be (regardless of experience level). There's a simple way to determine whether the above construct could define the variables in the if -- with a short, self-contained, compatible example (SSCCE):

#!/bin/python

if foo is not None:
    print okay

Running this yields an error:

Traceback (most recent call last):
  File "./test.py", line 3, in <module>
    if foo is not None:
NameError: name 'foo' is not defined

So, evidently this doesn't define foo. You are still stuck.

I know you aren't here for a lesson in programming. If I could give you a simple quick fix, I would. Unfortunately, there is not enough information for that because we still don't have the actual code you are running (or an SSCCE of it).

General programming questions actually belong on Stack Overflow; the community is much (much much) larger there and your problems really don't depend on anything particular about the the pi (it would be better if you approached this more abstractly, as with the SSCCE). The reality is that if you want to hack two scripts together, you do need to learn some basic concepts first. Find a "Learn Python in 24 Hours" type book, or work through a few tutorials online somewhere, whatever appeals to you. But doing things this way is beyond tedious for everyone involved, I think. You clearly cannot read code, at all, currently (even if you believe you sort of can).