How to "wow" someone new to Python

Matthew Ruffalo mmr15 at case.edu
Wed Jan 21 22:46:18 CET 2015


On 01/21/2015 04:26 PM, Chris Angelico wrote:
> On Thu, Jan 22, 2015 at 8:20 AM, Matthew Ruffalo <mmr15 at case.edu> wrote:
>> Yes, length-unlimited strings are *extremely* useful in some
>> applications. I remember bitterly cursing Java's string length limit of
>> 2 ** 31 (maybe - 1) on multiple occasions. Python's strings seem to
>> behave like integers in that their size is limited only by available memory.
> Hmm, I don't know that you'll get much beyond 2**31 characters (even
> all-ASCII characters in PEP 393) on a 32-bit Python, simply because
> "available memory" is capped at 2**32 bytes minus other stuff. You'd
> need a 64-bit Python to do that, and I would guess a 64-bit Java would
> also raise the limit.
>
> ChrisA
No, Java's String.length returns an int and Strings are limited to ~2 **
31 characters even in 64-bit Java.

I do seem to have encountered some strange behavior, though: creating
very large strings with str.__mul__ seems to enter an allocation loop in
Python 3.4. With a single-character string 's', I can create the
following new strings quickly:

s * 2 ** 33
s * 2 ** 34
s * 2 ** 35
s * 2 ** 36

but s * 2 ** 38 shows some odd memory usage. I'm watching the memory
usage of a Python process steadily increase to 256GB, drop to a few MB,
climb back to 256GB, drop to a few MB, and so on. It takes a half-dozen
cycles of allocation and deallocation before the interactive interpreter
gives me another prompt.

MMR...




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