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For 2023 (and 2024 ...) - 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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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))
Nested exceptions in Python

Yes, you can nest exceptions in Python - here's an example from yesterday's course.

I'm reading in lines from a data file and counting the numbe of occurrences of a particular series of events in a dictionary of dictionaries.

An exception is thrown if a counter doesn't already exist ... we'll catch that and create the extra counter if we have to ... excpet that ...

The incoming data line may be a short header, in which case we ignore it.

Here's the code:

import urllib

fh = urllib.urlopen("http://192.168.200.67/data/access_log.xyz")
counter = {}
goofs = 0

while 1:
  line = fh.readline()
  if not line: break
  hinfo = line.split(" ")
  try:
    counter[hinfo[6]][hinfo[0]] += 1
  except:
    try:
      counter[hinfo[6]] = {}
      counter[hinfo[6]][hinfo[0]] = 1
    except:
      pass
print counter
print "problem count =",goofs


Remember that in Python, you inset code to indicate your block structure, and that the pass statement can be used to create a do-nothing block.
(written 2007-01-18)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Y109 - Python - Exceptions
  [381] Exceptions in Python - (2005-07-17)
  [1236] Trying things in Python - (2007-06-18)
  [2018] UnboundLocalError - Python Message - (2009-01-31)
  [2281] Python - using exceptions to set a fallback - (2009-07-12)
  [2368] Python - fresh examples of all the fundamentals - (2009-08-20)
  [2408] Robust user input (exception handling) example in Python - (2009-09-17)
  [2622] Handling unusual and error conditions - exceptions - (2010-02-03)
  [2994] Python - some common questions answered in code examples - (2010-10-10)
  [2998] Using an exception to initialise a static variable in a Python function / method - (2010-10-13)
  [3177] Insurance against any errors - Volcanoes and Python - (2011-02-19)
  [3433] Exceptions - a fail-safe way of trapping things that may go wrong - (2011-09-11)
  [3441] Pressing ^C in a Python program. Also Progress Bar. - (2011-09-15)
  [3664] Error checking in a Python program - making your program robust via exceptions - (2012-03-22)
  [3913] How many times ... has this loco headed west through Tenby? - Python exceptions - (2012-11-05)
  [3930] Reporting the full stack trace when you catch a Python exception - (2012-11-22)
  [4029] Exception, Lambda, Generator, Slice, Dict - examples in one Python program - (2013-03-04)
  [4161] Python varables - checking existance, and call by name or by value? - (2013-08-27)
  [4444] Elements of an exception in Python - try, except, else, finally - (2015-02-28)


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Bounce, bounce, bounce
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Call for appropriate train services - Swindon, Bristol, Bath, West Wilts, Severn Beach etc
Sending an email from Python
Nested exceptions in Python
Learnt in London - Ruby, Martini, Coral and the Core
What the customer is looking for - effective training
Know to the police
Impact Engineering and Backscatter
Python Qt, wX, TkInter, and Jython - training??
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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