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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
Elements of an exception in Python - try, except, else, finally

All the elements of an exception handler in one example ... [here]

try - enters at the top and continues through the block
except - jump to there is an exception is thrown
else - run after the try block completes without exception thrown
finally - always run after the other blocks have completed

A correctly running block
try - else - finally
(and code loops completes)

  -bash-4.1$ python duff
  (bfor) Exception demonstration
  
  (try-) Please enter a Python value: 44
  (else) Input accepted
  (finl) Tidying up
  
  (done) Value received: 44
  -bash-4.1$


A block with an error
try - except - finally
(and code loops back to have another go)

  -bash-4.1$ python duff
  (bfor) Exception demonstration
  
  (try-) Please enter a Python value: forty
  (exce) Not acceptable!
  (exce) Message: name 'forty' is not defined
  (exce) Failure Type: NameError
  (finl) Tidying up
  
  (try-) Please enter a Python value:


Code

  while True:
    try:
      n = input("(try-) Please enter a Python value: ")
    except KeyboardInterrupt:
      print "(ex/k) You give up?"
      print "(ex/k) Won't break me that way"
    except Exception,e:
      print "(exce) Not acceptable!"
      print "(exce) Message: ",e
      print "(exce) Failure Type:",e.__class__.__name__
    else:
      print "(else) Input accepted"
      break
    finally:
      print "(finl) Tidying up\n"

(written 2015-02-28)

 
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)
  [1042] Nested exceptions in Python - (2007-01-18)
  [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)


Back to
Seventh stay away this year - and it's still only February!
Previous and next
or
Horse's mouth home
Forward to
Graphing presentations in Python - huge data, numpy and matplotlib
Some other Articles
What is the difference between a function and a method?
Overnight accommodation in Melksham - if Well House Manor is full!
Combining tests into suites, and suites into bigger suites - Python and unittest
Graphing presentations in Python - huge data, numpy and matplotlib
Elements of an exception in Python - try, except, else, finally
Seventh stay away this year - and it's still only February!
Mutable v Immuatble objects in Python, and the implication
Reading command line parameters in Python
A first graph with Matplotlib in Python
Json is the new marshall, pickle and cPickle / Python
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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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