Let's make this an unordered list by prefixing this line with a hyphen followed by a space. :)

Sure, but not sure what you mean

This will render as a list item:

- [PK](https://github.com/gae123)

Let's switch the branches to avoid the double negative.

Sorry, could you elaborate what you mean?

PK
http://www.gae123.com

Rather than…

if not cond:
    ...
else:  # if not not cond (double negative)
    ...

Let's write…

if cond:
    ...
else:  # if not cond
    ...

Does this need to be a global? Could we simply read the environment variable each time this function is invoked?

It does not need to be, but there is less overhead in reading a python variable than looking up an OS environment variable. So the code reads the environment variable only once and then we use that value in subsequent calls.

I don't know whether this overhead is significant, but if you want to avoid reading the environment variable multiple times you could use a closure:

def outer():
    ss = ...
    def inner(url, method, data):
        # ss is accessible here
    return inner
http_request = outer()

Avoid mutable default arguments. See http://docs.python-guide.org/en/latest/writing/gotchas/#mutable-default-arguments for details.