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POHow can I preserve or identify a caller's stack frame?
 

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  1. POHow can I preserve or identify a caller's stack frame?
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    <p>My brain feels slow today. </p> <p>I'm writing pre/post/invariants in Python using decorators. Currently, I need each call to specify the locals and globals for context, and this feels ugly. Is there a way to get the locals and globals from the decorator application level even though it's an arbitrary depth.</p> <p>That is, I'm trying to make this ugly code: from dectools import invariant, pre, post, call_if</p> <pre><code>@invariant("self.price &gt;= 0 and self.inventory &gt;= 0 and Item.tax_rate &gt;= 0") class Item(object): tax_rate = 0.10 # California. No property taxes on old property. @post("ItemDB.fetch(self) = (name, price)", locals(), globals()) def __init__(self, name, price): self.name = name self.price = price self.total_sold = 0 self.inventory = 0 @call_if(check_level, "manager") @post("self.total_sold &gt; 0", locals(), globals()) @pre("discount &gt; 0 and discount &lt;= self.price * 0.50", locals(), globals()) def adjust_price(self, adjustment): .... </code></pre> <p>into the same ugly code without all the "locals(), globals()". I run into problems where the nested decorators give me arbitrary stack depths, so my implementation of dectools.pre couldn't grab from a constant depth sys._getframe(). The stack is not something I've played with much, and would appreciate it if someone has a trick. (Yes, I'm hacking the local variables into the locals by assuming self will be in the right stack frame. It's the Item.tax_rate that is always out of scope, and self, and ItemDB.)</p> <p>Thank you in advance,</p> <p>Charles</p>
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    1. USCharles Merriam
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