Internet Speed Calculator
Your whole function get_seconds is not needed at all. You can use the function time.time(), which gives you the seconds since epoch (Jan 1, 1970 0:00:00). Subtracting two such times will yield the number of seconds passed in between. I would also do the time measurement exclusively around the actual download, otherwise you add the (small) overhead of reading the header for the file-size.

def downspeed():
    url = "http://speedtest.ftp.otenet.gr/files/test100k.db"

    start = time.time()
    file = requests.get(url)
    end = time.time()

    time_difference = end - start
    file_size = int(file.headers['Content-Length'])/1000    
    return round(file_size / time_difference)


You should also report the units of your speeds measured. As it is, they will be KB/s, with the K denoting 1000 (as you divide by that). You should be aware that there is also a different unit, sometimes written KiB/s, where Ki stands for 1024. You should probably use the same definition, which speedtest uses, when it says the file is 100kb big.