Why Aren't Globals Copied When I Run Eval With A Globals Argument?

I'm having difficulty understanding how eval() behaves regarding the globals used in the evaluated expression. For example, the following script prints 1: x = 1 print eval('x') Wh

Solution 1:

This appears to be a bug. Whether it's a bug in the documentation or the implementation, I don't know, but eval does not copy the current globals into globals if __builtins__ is not present. Rather, it only copies __builtins__:

if (PyDict_GetItemString(globals, "__builtins__") == NULL) {
    if (PyDict_SetItemString(globals, "__builtins__",
                             PyEval_GetBuiltins()) != 0)
        returnNULL;
}

I didn't find anything about this on the Python bug tracker, and the discrepancy is still present in 3.4 and the current dev branch, so it may be worth submitting a bug report and a proposed documentation correction:

If the globals dictionary is present and lacks ‘__builtins__’, the current __builtins__ is copied into globals before expression is parsed.