I was looking through code like this:

  foo = '%s%s%s' % ('https://', host, uri)

and realized this could be rewritten by the interpreter as:

  foo = 'https://%s%s' % (host, uri)

I tried to determine how much code this might affect, but it was pretty hard for me to come up with a decent regex to filter out all the false positives.  There were too many hits to determine if this would be used often.