[Tutor] about assert
alan.gauld at freenet.co.uk
alan.gauld at freenet.co.uk
Wed Sep 13 20:11:10 CEST 2006
>>Python manual has a very brief introduction
>>of "assert" statements. It is very difficult
First you probably don't need to use asserts
very often, they are useful if you are building
production strength code but for most users
of Python the exception mechanism is good enough.
Basically we use asserts to check pre and post
conditions as well as\ invariants in functions.
Anything other than that should be done using
explicit if/else or exceptions. The reason for
that is that asserts only operate when the code
is in debug mode... so they should not be
used for normal run time error detection.
Typical things to check are that input values
are within expected ranges and of desired types.
Also that the final retrurn value of a function
is within expected limits.
Once we finish testing the overhead of those
checks might not be required in the final
version if we are sure they will never
deviate from the test results.
The syntax can be demonstrated quite easily
and Luke has done that, the intent is a little
less obvious and IMHO really needs a larger
example to make the value obvious. Since I'm
at a cyber-cafe net terminal I dont feel like
trying that just now! :-)
HTH,
Alan G.
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