This week, we're updating our course layouts and descriptions. Presentation and materials always gently change over time, but just occasionally there's a need to make a step change to clear out some of the old and roll in the new. That's now happening - but over a long and complex site it's not instant and you'll see sections of the site changing up to and including 19th September.
See also [here] for status update
Robust user input (exception handling) example in Python
One of the questions in the "exceptions" section of the Python Course
asks my delegates to "Graham Proof" a piece of code:
first = int(input("First number: "))
second = int(input("Second number: "))
print "Sum is "+str(first+second)
The idea is that I come round the room and put really awkward inputs into customer's programs, as would a hacker or a non-thinking user. Not only is there a need to trap exceptions, but input should be changed to raw_input, and the input / error handling delegated to a function so that an error on the second input doesn't push the user back to remaking the first input, nor does it result in code duplication. Here is what I came up with:
result = raw_input(pr+" ")
val = float(result)
print "Ran out of Data"
first = getval("first number")
second = getval("second number")
print "Sum is "+str(first+second)
A further comment on the EOFError. On some systems, you can
continue to read even if you've received an EOF - RedHat Fedora Linux being one of them. On others, such as my Mac with OS X, reading past the end of file results in the code returning a further EOF without checking / waiting so see if there's any more data. My code above deals with the case on both types of operating system ... (written 2009-09-17, updated 2009-09-20)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articlesY109 - Python - Exceptions 
Python varables - checking existance, and call by name or by value? - (2013-08-27) 
Exception, Lambda, Generator, Slice, Dict - examples in one Python program - (2013-03-04) 
Reporting the full stack trace when you catch a Python exception - (2012-11-22) 
How many times ... has this loco headed west through Tenby? - Python exceptions - (2012-11-05) 
Error checking in a Python program - making your program robust via exceptions - (2012-03-22) 
Pressing ^C in a Python program. Also Progress Bar. - (2011-09-15) 
Exceptions - a fail-safe way of trapping things that may go wrong - (2011-09-11) 
Insurance against any errors - Volcanoes and Python - (2011-02-19) 
Using an exception to initialise a static variable in a Python function / method - (2010-10-13) 
Python - some common questions answered in code examples - (2010-10-10) 
Handling unusual and error conditions - exceptions - (2010-02-03) 
Python - fresh examples of all the fundamentals - (2009-08-20) 
Python - using exceptions to set a fallback - (2009-07-12) 
UnboundLocalError - Python Message - (2009-01-31) 
Trying things in Python - (2007-06-18) 
Nested exceptions in Python - (2007-01-18) 
Exceptions in Python - (2005-07-17)
Some other Articles
Autumn Fruits and Bristol Old StationFurther North - long summer days and lovely countrysideRemoval of technical resources from this siteTypeError: super() argument 1 must be type, not classobj (Python)Robust user input (exception handling) example in PythonTesting code in Python - doctest, unittest and othersPound Sign in Python ProgramBut I am reading from a file - no need to prompt (Perl)Low Sun - Autumn is hereHotel Booking Scam / Cost of calls to 070 numbers
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