For 2023 - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.
Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!
I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Reporting the full stack trace when you catch a Python exception
Python exceptions are a safety net which let you catch data or program problems or other unexpected issues without having to explicity code each and every potential problem or problem group - a wonderful fail safe mechanism.
If you fail to write your Python code with try
blocks, it will use the default (built in) exception handler, which give you a full stack trace (a confession) and exits the program. Thus
a = 6 /0
wizard:nov12 graham$ python tiny
Traceback (most recent call last):
File "tiny", line 3, in
File "tiny", line 2, in doit
a = 6 /0
ZeroDivisionError: integer division or modulo by zero
Within your own exception handlers ...
• you can pick up your exception object and generate your own message.
• you can use the message
objects to report Python's own message and class name
• you can use the traceback
module to print out a full confession
Here's a code snippet showing you the standard and traceback items in use:
A full example including traceback use from yesterday's Intermediate Python Course
. (written 2012-11-22, updated 2012-11-24)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articlesY109 - Python - Exceptions 
Exceptions in Python - (2005-07-17) 
Nested exceptions in Python - (2007-01-18) 
Trying things in Python - (2007-06-18) 
UnboundLocalError - Python Message - (2009-01-31) 
Python - using exceptions to set a fallback - (2009-07-12) 
Python - fresh examples of all the fundamentals - (2009-08-20) 
Robust user input (exception handling) example in Python - (2009-09-17) 
Handling unusual and error conditions - exceptions - (2010-02-03) 
Python - some common questions answered in code examples - (2010-10-10) 
Using an exception to initialise a static variable in a Python function / method - (2010-10-13) 
Insurance against any errors - Volcanoes and Python - (2011-02-19) 
Exceptions - a fail-safe way of trapping things that may go wrong - (2011-09-11) 
Pressing ^C in a Python program. Also Progress Bar. - (2011-09-15) 
Error checking in a Python program - making your program robust via exceptions - (2012-03-22) 
How many times ... has this loco headed west through Tenby? - Python exceptions - (2012-11-05) 
Exception, Lambda, Generator, Slice, Dict - examples in one Python program - (2013-03-04) 
Python varables - checking existance, and call by name or by value? - (2013-08-27) 
Elements of an exception in Python - try, except, else, finally - (2015-02-28)
Some other Articles
Multiple identical keys in a Python dict - yes, you can!Behind Melksham Spa - Mood Mist over wet fields.River nearly bursting its banks in MelkshamOptional positional and named parameters in PythonReporting the full stack trace when you catch a Python exceptionMelksham Bus Issues - to be raised at First Bus Customer PanelStoring your intermediate data - what format should you you choose?First match or all matches? Perl Regular ExpressionsFiltering PHP form inputs - three ways, but which should you use?Red sky at night
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This is a page archived from The Horse's Mouth at
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