import time
def is_url(url):
"""
Test whether argument is url
"""
url = url.rstrip()
if len(url.splitlines()) > 1:
return False
if url.find(' ') >= 0:
return False
return (
url.startswith('http://') or
url.startswith('https://') or
url.startswith('ftp://')
)
def retry(func, exc=Exception, tries=3, delay=1):
"""
Call ``func()`` up to ``tries`` times, exiting only if the function
returns without an exception. If the function raises an exception on
the final try that exception is raised.
If given, ``exc`` can be either an `Exception` or a tuple of `Exception`s
in which only those exceptions result in a retry, and all other exceptions
are raised. ``delay`` is the time in seconds between each retry, and
doubles after each retry.
"""
while True:
try:
return func()
except exc:
tries -= 1
if tries == 0:
raise
time.sleep(delay)
delay *= 2
