How do you gracefully handle failed future feature imports? If a user is running using Python 2.5 and the first statement in my module is:

from __future__ import print_function

Compiling this module for Python 2.5 will fail with a:

  File "__init__.py", line 1
    from __future__ import print_function
SyntaxError: future feature print_function is not defined

I'd like to inform the user that they need to rerun the program with Python >= 2.6 and maybe provide some instructions on how to do so. However, to quote PEP 236:

The only lines that can appear before a future_statement are:

  • The module docstring (if any).
  • Comments.
  • Blank lines.
  • Other future_statements.

So I can't do something like:

import __future__

if hasattr(__future__, 'print_function'):
    from __future__ import print_function
else:
    raise ImportError('Python >= 2.6 is required')

Because it yields:

  File "__init__.py", line 4
    from __future__ import print_function
SyntaxError: from __future__ imports must occur at the beginning of the file

This snippet from the PEP seems to give hope of doing it inline:

Q: I want to wrap future_statements in try/except blocks, so I can use different code depending on which version of Python I'm running. Why can't I?

A: Sorry! try/except is a runtime feature; future_statements are primarily compile-time gimmicks, and your try/except happens long after the compiler is done. That is, by the time you do try/except, the semantics in effect for the module are already a done deal. Since the try/except wouldn't accomplish what it looks like it should accomplish, it's simply not al

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