Store and retrieve values from text file [python]

Question

Environment :Unix Python version : 2.7

I have a scenario where I am fetching some amount of data from an API and then storing it in a text file. I am running the python script with scheduled cron jobs of interval 30 minutes. while running it if the value of count is increased by 1 the previous value is changed to recent increased/decreased count if not then it runs same. what I am trying to implement is if the count is increased on first run it I will store the value temporarily then again on next run after 30 minutes comparison should happen with the previous value not the recent increased/decreased count, and then if the count is still increased/decreased then store it permanently and proceed further.

code

def app_counts():

    while True:
        try:
            url_node = os.popen("ApiURL").read()
            node_data = json.loads(url_node)
        except BaseException as exp:
            continue
        break
    process_num = (node_data[0]["proc"])
    node_count = len(process_num)
    print ("...........................................")
    f_check = file("/home/user/app_check/file.txt",'r')
    f_data = f_check.read()
    chk_data = int(f_data)
############################write increased count to file######################################################
    f1 = open("file.txt", "w")
    n1 = f1.write(str(node_count) + "\n")
    f1.close() #Here I want to store the current increased count temporarily(for example if count is increased/decreased store it temporarily and from next run compare it from previous one still if it is increased then store permanently)

def app_acc():
    comp_n = recent_node_counts()
    f2 = file("/home/user/app_check/file.txt",'r') ## reads last value of count
    r_data = f2.read()
    cmp_n = int(r_data)
    if(comp_n < cmp_n ):

          sys.exit(1) ### fail the build forcefully
    else:
          print ('OK ')
          print 'recent count = ', comp_n

I am new to python can anybody help to acheive this ,what should I use in order to achieve this.

Answer 1

Your json file will look something like this

{
    "latest": 5,
    "history": [1, 2, 3, 4]
}

Basically, I am storing the recent node counts value as latest and maintaining the history (recent ones get appended at the end of it).

import json


def get_data():
    # read json file data from previous run
    with open("/home/user/app_check/file.txt") as f_check:
        data = json.load(f_check)
    return data


def app_counts():
    ...
    node_count = len(process_num)
    ...
    data = get_data()
    # if value is increased from last, store it permanently
    if data['latest'] < node_count:
        data['history'].append(node_count)
    # update latest temporary count
    data['latest'] = node_count
    # write to json file
    with open("file.txt", "w") as f1:
        json.dump(data, f1)


def app_acc():
    comp_n = recent_node_counts()
    data = get_data()
    if(comp_n < data['latest']):
        sys.exit(1) ### fail the build forcefully
    else:
        print ('OK ')
        print 'recent count = ', comp_n