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POHow do I recover an older traceback in python? (eg second to last)
 

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  1. POHow do I recover an older traceback in python? (eg second to last)
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    <p>I'm sure you found yourself in this situation, and I suspect there is no way out of this. Suppose you run some python code that raises an exception, then you want to look into it but accidentally raise <strong>another</strong> exception while doing so. If you try postmortem debugging now, you'll see the traceback of the latter exception. My question is, is the former lost forever?</p> <p>Example:</p> <pre><code>def my_buggy_function(x): y = x + 1 raise RuntimeError </code></pre> <p>Step 1: I raise an error and I want to debug it</p> <pre><code>my_buggy_function(1) --------------------------------------------------------------------------- RuntimeError Traceback (most recent call last) /home/user/&lt;ipython-input-1-430423eaff77&gt; in &lt;module&gt;() 3 raise RuntimeError 4 ----&gt; 5 my_buggy_function(1) /home/user/&lt;ipython-input-1-430423eaff77&gt; in my_buggy_function(x) 1 def my_buggy_function(x): 2 y = x + 1 ----&gt; 3 raise RuntimeError 4 5 my_buggy_function(1) RuntimeError: </code></pre> <p>Step 2: I try to debug the error but accidentally raise another one (in this case, I did not load pdb)</p> <pre><code> pdb.pm() #Oops.. --------------------------------------------------------------------------- NameError Traceback (most recent call last) /home/user/&lt;ipython-input-2-619d77b83f20&gt; in &lt;module&gt;() ----&gt; 1 pdb.pm() NameError: name 'pdb' is not defined import pdb </code></pre> <p>Step 3: Now the traceback gives me the last error, and the second to last is lost.</p> <pre><code> pdb.traceback.print_last() Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/IPython/core/interactiveshell.py", line 2538, in run_code exec code_obj in self.user_global_ns, self.user_ns File "&lt;ipython-input-1-619d77b83f20&gt;", line 1, in &lt;module&gt; pdb.pm() NameError: name 'pdb' is not defined </code></pre> <p>What if I want to access y in the second-to-last traceback, is it lost forever?</p> <p>Note: I'm using ipython/ipdb in case it matters </p>
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    1. COI believe you might be able to access the *last* traceback via ``sys.last_traceback`` -- Give that a go and let me know. I can't reproduce your scenario exactly as I don't use IPython myself.
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    2. CO@JamesMills When a new exception occurs, won't `last_traceback` point to that one?
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    3. COThere is also ``sys.exc_tracback`` (*the current traceback being handled*) -- so the ``sys`` documentation leads me to believe that this *might* work.
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