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GOAL
I am trying to compile an AST which contains an ImportFrom node which performs a __future__ import. The ImportFrom node in question is the first node within the AST's body (as it should be, because __future__ imports must occur at the beginning of modules).
ISSUE
Compiling the AST fails with the error "SyntaxError: from __future__ imports must occur at the beginning of the file".
ANALYSIS
The future_parse() function in future.c looks for __future__ imports and identifies them based on the condition (ds->v.ImportFrom.module == future) where future is constructed using PyString_InternFromString("__future__"). That is, the module attribute of the ImportFrom node is compared by identity with the interned string "__future__".
The AST which I was compiling used the string "__future__" after extracting that string from a much longer string of user input, and as a result, the string was not interned.
The attached file futureimport.py is a simple script demonstrating this issue. I have confirmed that the issue occurs in Python 2.7.2 and 3.2.2.