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Optimizing code

Harald Hanche-Olsen hanche at math.ntnu.no
Fri Feb 25 10:28:47 EST 2000 
+ Gerrit Holl <gerrit.holl at pobox.com>:

| >   File "du.py", line 21, in du
| >     return len(disk)
| > TypeError: __len__() should return an int
| 
| A long? I don't see any long?

Because I didn't show it to you.  8-)

| Perhaps you are running a "future" version of Python silently
| converting ints to longs?

Nah.  It's plain vanilla 1.5.2.  But this is on a FreeBSD 3.3 machine,
where file sizes and offsets are specified using 64 bit integers.
Since they don't fit into a (32 bit) python int, python evidently
decides to make them all long ints, whether that is needed or not.

| And, by the way, why can't len() return a long integer?

Presumably because the address space is still 32 bits, and no object
in memory can conceivably be longer than 2**32.  (In any case I found
your use of __len__ to be slightly offensive.)  But wait, you sure
*could* imagine an object longer than 2**31, and since python ints are
signed, then len() would turn out to be negative.

so-more-than-2GB-of-swap-could-get-you-into-trouble-ly y'rs,
-- 
* Harald Hanche-Olsen     <URL:http://www.math.ntnu.no/~hanche/>
- "There arises from a bad and unapt formation of words
   a wonderful obstruction to the mind."  - Francis Bacon
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