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Comment by dec0dedab0de | Hacker News Reader

What I'm describing was just a desire for a very simple "this script requires python version >= X" error, with the ability to write unfettered python version X code below it, in a single file script.

  import sys
  if sys.version_info.major < 3:
    raise Exception("this script requires python version >= 3")

plus an extra line or two if you're worried about minor versions.

View on HN

  > cat test.py 
  import sys
  if sys.version_info.major < 3:
      raise Exception("this script requires python version >= 3")
  
  print(f"test")
  
  > python2 test.py
    File "test.py", line 5
      print(f"test")
                  ^
  SyntaxError: invalid syntax

Doesn't seem that simple

It needs to also do:

   from __future__ import absolute_import, division, print_function, unicode_literals

This will give you syntax much closer to Python 3 in Python 2.7. The remaining differences can be papered over with function and class helpers. Well, except for metaclasses, but I doubt you'd have need for those in a single-file script.

Now put an f-string (or other new feature that pops a syntax error) below that:

print(f"whee")

And run it with python2, or a python3 < 3.6.

ahh, I see now. I would add an edit to my original comment, but it's too late.

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