Are you used to writing long sections of code to validate user input? Perhaps you are, or perhaps you have shortened such code over the years using Regular Expressions
where you can specify a pattern to be matched. One regular expression can replace 30 lines of other code.
But in Python, Java and some other languages there's an even more elegant alternative in some circumstances - exceptions. The idea is that you try
to perform the action you require on your input data rather than 100% validating it first. If the action works, great and if it fails you catch
and handle the error condition in that block.
Like an example? Here's a piece of Python code to read an integer from the program's user, and to keep re-prompting if the user enters a value that cannot be treated as a legitimate integer.
while 1: (written 2007-06-18)
val = raw_input("give an integer ... ")
ival = int(val)
print "an integer is a WHOLE NUMBER! "
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) 
Robust user input (exception handling) example in Python - (2009-09-17) 
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) 
Nested exceptions in Python - (2007-01-18) 
Exceptions in Python - (2005-07-17)
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