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POHow to access globals from a different point in code
 

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    <p>I'm trying to find a way of basically doing a late <code>eval</code>, using context from a different location in the code. As an example, I have a class <code>Friend</code>, and it can be used like this:</p> <pre><code>&gt;&gt;&gt; class A: ... friend = Friend('B') ... &gt;&gt;&gt; class B: ... friend = Friend('A') ... &gt;&gt;&gt; A.friend.getobject() &lt;class '__main__.B'&gt; </code></pre> <p>However, <code>Friend</code> is defined elsewhere in the code, in a separate library, and would look something like this:</p> <pre><code>class Friend: def __init__(self, objname): self.objname = objname def getobject(self): return eval(self.objname, original_context) </code></pre> <p>The sqlalchemy ORM has a similar pattern for defining columns, but they implement it by tracking all owning classes (i.e. tables) in a session. I could do something similar if I need to, but I'd like to know if there is another way to do this. I've been looking at frames and the interpreter stack, and I think I can get to the relevant frame's locals using something like <code>inspect.stack()[1][0].f_locals</code>, but I would have to do this in <code>Frame.__init__</code> which is called before the object is defined.</p> <p>My questions is how to find <code>original_context</code>, but only at the time it is needed. This comes down to two issues: 1. How to access the environment (or frame?) in which <code>Friend</code> was instantiated. 2. How to access it at the time <code>getobject</code> is called.</p>
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