Entry

How can I make my assertions smarter?

Jul 5th, 2000 10:02
Nathan Wallace, Hans Nowak, Snippet 265, Magnus L. Hetland

"""
Packages: miscellaneous
"""
"""
> I'm using some simple functions to implement crude precondition,
> postcondition and invariant checking in Python classes.
> 
> (Tim: please be gentle ;-)
> 
> Is there some neat way to wrap these tests up so I can print any
> code expression that fails, e.g:
> 
>      Precondition failed foo.py line 42: spoon.shape == 'bent'
> 
> which would appear at line 42 of foo.py as
> 
>      pre(spoon.shape == 'bent')
How about using (assuming that you won't use assert):
       pre("spoon.shape == 'bent'")
And then using eval() in your code? Like...
"""
def pre(condition):
    if not eval(condition):
        raise "Precondition Failure", condition
"""
Pretty simple, IMO...
"""