Could Python supplant Java?
bdesth at nospam.free.fr
Wed Aug 21 07:06:59 CEST 2002
> laotseu <bdesth at nospam.free.fr> wrote in message news:<3D61A538.2050107 at nospam.free.fr>...
>>I used to think the same (what about VB's 'variant' ? yuk !)... But
>>python's dynamic typing has got me, specially in the case of oo
>>programming. It makes polymorphism a really simple thing.
> And more dangerous :-)
What is the more dangerous : relying on the compiler or knowing what you
do when wrting code ? It's more about the way you work than about the
language you use.
>>IMHO, compile time type-checking is a nice safety net, but if you get a
>>type error at compilation, it still means you made a mistake.
> Yes, but the error is flagged in compilation, as opposed to
> five weeks after the product ships, when it crops up in a bug
> report from a customer.
Programs *should* be tested before shipping
(ok, I know it's a dream but... )
> Strong and weak typing have their place.
What has strong or weak typing has to do with this ? Python is strongly
typed. The fact that an *identifier* has no type by itself doesn't mean
that the *object* is refers to doesn't have one.
> Dynamic types are less
> hassle to work with, but of course they push an added burden of
> testing onto the developer
No. Write (good) tests first, then write your code, then let the
computer run the tests.
> - because mistakes are not so easily
Your compiler won't spot most of the mistakes. Well written tests will.
> However, for languages targetted maining at scripting
> (scripts tend to be brief by their very nature) then the added
> burden of dynamic typing is managable, and the benefits often
> outweigh the problems.
> This is one of the reasons why I do not consider Python a suitable
> alternative to Java. Dynamic typing is fine for scripts, but when
> it comes to full-blown 'ten thousand line' applications you really
> should be looking as something IMHO which gives you the added
> security of strong typing, to catch as many potential bugs as
Ok. Objective C has dynamic typing. Whole Operating systems have been
written in Objective C. Would you consider that :
- Objective C is not suited for anything else than scripting ?
- Java would be a sensible choice for writing an OS ?
(NB : I'm *not* suggesting Python would be a good choice if you plan to
write an OS)
>>in C, you can have type error when casting a void*, and you don't have
>>any info about the original type of the pointeur. Dynamic typing doesn't
>>means Python is not *strongly* typed.
> Surely the two are mutually exclusive? Unless this is some very
> novel use of the word 'strongly'? :-)
No. Dynamic typing doesn't not imply weak typing. C has static, but
relativly weak typing : use a cast, and the compiler will accept anything.
int answer = 42;
char *meaning_of_life = (char *)answer; /* compiler is happy */
(tested with gcc -Wall -pedantic).
So static doesnt means strong.
Now when it comes to 'polymorphism' (or at least some kind of...), C
uses void *. But once you cast to void *, there is no way to know the
original type of the pointer :
void funcA(void *meaning_of_life)
/* we just can hope that the caller passed the good type */
char *marvin = (char *)meaning_of_life;
/* now cross fingers and run */
[snip some code that tries & modify marvin[strlen(marvin) - 1] ]
int answer = 42;
* oh, shit, I'm to (lazy || tired || in a hurry) to check
* the correct type
/* system crash ! Too bad */
Get it ?
In Python, when you code :
/> toto = 0 + 0
the identifier toto is bound to an integer object.
Now when you code :
/> toto = 'la tête à toto'
toto is bound to a string object.
The *identifier* toto has no type by itself, but the *object* it is
bound to does have one, and you can easily know which.
This is, AFAIK, the difference between strong vs weak and dynamic vs
(Please someone correct me if I'm wrong)
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