如何确定 Python 模块是否在 GAE 上运行？

Question

I have a module that uses lxml. Since this cannot be imported on GAE, I'd like to use a suitable substitute by default. Something along the lines of:

if not ON_GAE:
    import lxml
else:
    import beautifulsoup

How can I determine that I'm on GAE? Is there a OS variable of some sorts?

Update: There are certain modules that will not run on GAE (like sockets ). Rather than having multiple blocks of try ... except ImportError , I'd like to know from the start which code blocks needs an alternative implementation.

Answer 1

You can use this:

on_app_engine = os.environ.get('SERVER_SOFTWARE', '').startswith('Google')

Then something like:

if on_app_engine:
  import lxml
else:
  import bla

Answer 2

You can simply try and see if an import throws an exception and use the other import only if it's necessary.

try:
    import lxml
except ImportError:
    import beautifulsoup