Welcome at SO
You have two options
Let Python code decide on name of output file
This will likely be based on current time, e.g.
import time
# here get somehow your page content
page_content = ?????
prefix = "outut-"
suffix = ".html"
fname = "{prefix}{now:d}{suffix}".format(now=time.time())
print fname
with open(fname, "w") as f:
f.write(page_content)
Let your external loop (out of Python) create the file name
This file name can be e.g. on Linux created by some form of date
command.