How to handle AssertionError in Python and find out which line or statement it occurred on

Question

I want to handle AssertionErrors both to hide unnecessary parts of the stack trace from the user and to print a message as to why the error occurred and what the user should do about it   Is there any way to find out on which line or statement the assert failed within the except block   try      assert True     assert 7    7     assert 1    2       many more statements like this except AssertionError      print  Houston  we have a problem       print     print  An error occurred on line      in statement          exit 1    I don t want to have to add this to every assert statement   assert 7    7   7    7    because it repeats information

User · Accepted Answer

Use the traceback module   import sys import traceback  try      assert True     assert 7    7     assert 1    2       many more statements like this except AssertionError            tb   sys exc info       traceback print tb tb    Fixed format     tb info   traceback extract tb tb      filename  line  func  text   tb info -1       print  An error occurred on line    in statement     format line  text       exit 1

User · Answer

The traceback module and sys exc info are overkill for tracking down the source of an exception  That s all in the default traceback  So instead of calling exit 1  just re-raise   try      assert  birthday cake      ice cream cake    Should ve asked for pie  except AssertionError      print  Houston  we have a problem       raise   Which gives the following output that includes the offending statement and line number   Houston  we have a problem  Traceback  most recent call last     File   tmp poop py   line 2  in  lt module gt      assert  birthday cake      ice cream cake    Should ve asked for pie  AssertionError  Should ve asked for pie   Similarly the  logging module makes it easy to log a traceback for any exception  including those which are caught and never re-raised    import logging  try      assert False    True  except AssertionError      logging error  Nothing is real but I can t quit      exc info True

[python] How to handle AssertionError in Python and find out which line or statement it occurred on?

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