Compare old and new values python

Question

When I am comparing two urls through if else i am getting always else (Prints test2), doesnt matter if two values are same. Why? Code is:

def derpypost():
    threading.Timer(10.0, derpypost).start()
    print(Fore.CYAN + Style.BRIGHT + "Прошло " + times +
          " минут, начинаю постить картинку в " + vk_group_name)
    print("   Получаю URL картинки")
    real_dp_tags = dp_tags.replace("'", "").replace("'", '')
    for image in Search().query(real_dp_tags).limit(1):
        url = image.image
        source = image.url
        post_tags = image.tags
        sourceurl = image.source_url
    old_url = open('compare.txt', 'r')
    print(old_url.read())
    olded_url = old_url.read()

    if olded_url == url:
        print("test")
    else:
        print('test2')
    old_url.close()
    with open('compare.txt', 'w') as f:
        f.write(url)
        print('WRITTEN!' + url)
        f.close()
derpypost()

In compare.txt is - https://example.com/ In url variable - https://example.com

Answer 1

This:

old_url = open('compare.txt', 'r')  # stream at pos 0
print(old_url.read())               # stream at end of file
olded_url = old_url.read()          # nothing to put into variable

will not work. Files are stream based, as soon as you consume them once the stream is at the end of the file.

Use

def writeFile(urlToWrite):
    fn = 'compare.txt'
    with open(fn, 'w') as createFile:
        createFile.write(urlToWrite)
        print("Wrote: " + urlToWrite)  # if you want it to see on console.

def readFile():
    fn = 'compare.txt'
    old_url = ""
    try:
        with open(fn, 'r') as rf:
            old_url = rf.read()
            print("Read: " + old_url)  # if you want it to see on console.
    except FileNotFoundError: # create file if not exists
        writeFile("")
    return old_url

curr_url = "tata"
old = readFile()
if old != curr_url:
    writeFile(curr_url)

Output (after 1st using tata, then tattoo for curr_url):

Read: tata
Wrote: tattoo