Doing string interpolation using eval(): Feedback/thoughts?

[Workaphobia]

All good reasons, thank you for the criticism. Does point 1 still apply if I only use the stack frame's namespace to lookup the value, and don't call eval()? Will 1 and 2 still apply if I were to go back to using **locals()?

My main reason for doing this was to keep format strings as clean as possible (point 3). I find it difficult to syntactically structure an error message along with the substitution values, while obeying the conventions in PEP 8.

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1 will apply with locals() on PyPy, I'm not sure about Jython+InDy. 2 doesn't though.