Terry J. Reedy added the comment:

Easy test case using -c:
\python_d.exe -m idlelib.idle -c "from __future__ import division; print(1/2)"
>>> 
0.5
>>> 1/2
0
>>> division
_Feature((2, 2, 0, 'alpha', 2), (3, 0, 0, 'alpha', 0), 8192)

Replace "-m idlelib.idle" with "-i" to get interactive interpreter and >>> 1/2 
is .5 instead of 0.

---
Implementation of -s in PyShell.py
if o == '-s': startup = True  # line 1504
if startup:  # line 1586
    filename = ...
    if filename ...
        ... execfile(filename)
execfile (line 650) is the same method used to run -c and -r code. After 
compiling code, it calls runcode (779). That normally sends the code to the 
user process, but may run code in the debugger or in the idle process.  When 
the future import is run, it is just an import and not also a 'from __future__' 
statement.

Editor files are compiled in ScriptBinding.ScriptBinding.checksyntax.  This is 
why not affected by __future__ import in PyShell (#24222).  Run_module_event 
calls (interp.)runcode, as above.

I believe Shell input is run by .runsource, which is called by .runit, which is 
called when appropriate by the <enter> callback.

.runsource in turn calls the base class method 
code.InteractiveInterpreter.runsource, which uses 'self.compile', which is an 
instance of codeop.CommandCompiler.  codeop.CommandCompiler indirectly uses 
'self.compiler', which is an instance of codeop.Compiler.  The latter is what 
actually calls the builtin function compile, with self.flags (futures 
imported), it updates self.flags from the flags in the code returned by compile.

So I believe the solution is for the ExtendedInterpreter instance to get a 
reference to the Compiler instance, after InteractiveInterpreter is 
initialized, and call that, with symbol='exec' instead of 'single', instead of 
calling compile directly.

A reason not to use the same pipeline as for statements enter interactively is 
that there is extra code to account for the possibility of compiling correct 
partial statements. "while True:\n" is not an error at a prompt, since more may 
follow, but is as a complete code string.

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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue22893>
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