Python script stops running in crontab after sometime

Question

I have a code which runs i am running in crontab on startup in Raspberry pi(The code runs fine in python "idle"). It has an infinite while loop in it. After sometime the python script stops running. i searched the net and got the following answers that could cause them

1. https://serverfault.com/questions/399029/python-script-stops-responding-when-run-for-a-long-time
2. http://www.solutionoferror.com/python/cron-jobbin39-a-python-script-stops-halfway-through-20824.asp (NO REPLY TO THIS ONE)
3. Cron jobbin' a python script: stops halfway through

At this point I am really confused about what is the reason behind it. I need help in understanding the reason behind this. And also what is the best way to run this code on start up of raspberry pi. Are there any tweaks required for crontab or is there some other method? Please reply elaborately as i am an EE major and not very familiar with linux, raspberry pi(since i have just started using it) and python. The code is as follows:

import threading
import os
import time
import serial
import httplib
import math

#GPS data
os.chdir('/home/pi/Desktop')

#Distance function
def Distance(lat1, long1,lat2,long2):

    degree_to_rad = float(math.pi / 180.0)

    d_lat = (lat2 - lat1) * degree_to_rad
    d_long = (long2 - long1) * degree_to_rad

    a = pow(math.sin(d_lat / 2), 2) + math.cos(lat1 * degree_to_rad) * math.cos(lat2 * degree_to_rad) * pow(math.sin(d_long / 2), 2)
    c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a))
    km = 6367 * c
    mi = 3956 * c

    return km

#global variables
global ser
global recieveBuffer
global recieveFlag
global webAddress
global data

#Serial Communication Settings
baud = 9600;
#port = 'Com4'
port ='/dev/ttyAMA0'

#default WebAddress and Data
webAddress = "gpsmaster.eu5.org"
webData = "/post.php?"

#Lat and Lng Coordinates, Initialied at Gate
lat=31.470997
lng=74.411116
lumsLat=31.470997
lumsLng=74.411116


ser = serial.Serial(port, baud)
if not ser.isOpen():
    ser.open()


recieveBuffer="NULL"
recieveFlag=0

def shutDown():
    os.system("sudo shutdown -h now")

def readSerial():
    global recieveBuffer
    global recieveFlag
    global ser
    while True:
        recieveBuffer = ser.readline()
        recieveFlag=1

# Function to Post Data, Return Y for success, N for failure
def httpGet(webAddress,webData):
    try:
        #print(webAddress)
        #print(webData)
        conn = httplib.HTTPConnection(webAddress)
        conn.request("GET",webData)
        res = conn.getresponse()
        #print res.status, res.reason
        conn.close()
    except:
        print("Exceptoion!!")
        return ['N','Failed']
    else:
        return ['Y',res]


def replayMaster(ser,recieved):
    global lat
    global lng
    recieved=recieved.replace("\n", "")
    recieved=recieved.replace("\r", "")
    tokenized = recieved.split(',');
    command = tokenized[0]
    if command=='AT':
        ser.write('<OK>')
    elif command=='POST':
        if lat!=0 and lng != 0: # and Distance(lumsLat,lumsLng,lat,lng)<50
            lat = float(tokenized[1])
            lng = float(tokenized[2])
            ans = httpGet(webAddress,"%slat=%f&lng=%f" % (webData, lat,lng))
            #with open("logFile.txt","a") as fileStream:
             #   fileStream.write("%s,%f,%f\r\n" % (ans[0],lat,lng))
            #fileStream.close()
            if ans[0]=='N':
                ser.write('<ERROR>')
            else:
                ser.write('<'+`ans[1].status`+'>')
        else:
            ser.write('<Invalid Coordinates>')
            print ("Invalid Coordinates")
    elif command=='CLOSE':
        ser.close()
    elif command=='HALT':
        ser.write('<Shutting Down>');
        shutDown()
    else:
        ser.write('<Unknown Command>')


serialReadThread = threading.Thread(target=readSerial)
serialReadThread.start()


ser.write('<OK>')
while True:
    #p#rint Distance(31.470997,74.411116,31.469723,74.512244)
    if recieveFlag:
        replayMaster(ser,recieveBuffer)
        print(recieveBuffer)
        recieveFlag=0
    print("waiting: |%f|,|%f|"%(lat,lng))
    time.sleep(0.4)

Answer 1

I had some issues with the crontab too. I fixed it with using a short time delay after reboot.

@reboot (sleep 10; python3 ABSOLUTE_PATH/example.py)

Maybe this could help