Can't import annotations from __future__

Question

When running the statement

from __future__ import annotations

I get the following error:

Traceback (most recent call last):
  File "/usr/lib/python3.5/py_compile.py", line 125, in compile
    _optimize=optimize)
  File "<frozen importlib._bootstrap_external>", line 735, in source_to_code
  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
  File "./prog.py", line 1
    from __future__ import annotations
    ^
SyntaxError: future feature annotations is not defined

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.5/py_compile.py", line 129, in compile
    raise py_exc
py_compile.PyCompileError:   File "./prog.py", line 1
    from __future__ import annotations
                                     ^
SyntaxError: future feature annotations is not defined

What could be the cause of this error?

Solution

Looking at your error traceback, it looks like you are using python 3.5. Is that the case?

If so, then the error happens because according to PEP-563 the import of __future__ annotations is available starting with Python 3.7.

I did not find any hints that this will be backported to previous versions, but I might have missed that.