does lack of type declarations make Python unsafe?

[Peter Hansen]

Donn Cave wrote:
> 
> One would think from reading this thread that this would be good
> for safety but hard to program for, but it's actually the opposite.
> I'm told that type checking is practically irrelevant to safety
> critical standards, because the testing needed to meet standards
> like that makes type correctness redundant.  

I haven't directly worked in aviation software myself, but a friend
(who is beginning to use Python more) who works in that area has
described much of his employer's development environment to me.

One interesting thing is that C is the mainstay language, and we
all know how type-safe it is.

Definitely the near-onerous testing requirements, as well as the
traceability permeating every aspect of the development from 
requirements to delivery, are what give the regulatory agencies
the necessary level of confidence to allow the software to be
released, not the use of type-safe languages.  (So far... but I
wouldn't be surprised to see bureaucratic/ivory-tower thinking
lead to a change in this policy.  Probably already happening... :-( )

-Peter