compress string of data

[José Carlos]

Hi.

How i could compress string of data?.

I heart that it´s possible to make with librep, but i´dont know the way to
do it.

if somebody know any way to do it or any web where explain it i would thank
the help.

Regards.

José Carlos
ADV
www.siadv.com

[Irmen de Jong]

José Carlos wrote:

How i could compress string of data?.

Type "python compress string of data" in google and press "I'm feeling lucky".
That might help you out.

--Irmen

[Gerrit Holl]

> How i could compress string of data?.

import zlib
zlib.compress("Hello, world")

'x\x9c\xf3H\xcd\xc9\xc9\xd7Q(\xcf/\xcaI\x01\x00\x1b\xd4\x04i'

http://www.python.org/doc/current/lib/module-zlib.html

Gerrit.

[Piet van Oostrum]

>>>>> Gerrit Holl <ge****@nl.linux.org> (GH) wrote:

How i could compress string of data?.

import zlib
zlib.compress("Hello, world")

GH> 'x\x9c\xf3H\xcd\xc9\xc9\xd7Q(\xcf/\xcaI\x01\x00\x1b\xd4\x04i'

GH> http://www.python.org/doc/current/lib/module-zlib.html

Waw, that compresses it from 12 bytes to 20 bytes :=)
--
Piet van Oostrum <pi**@cs.uu.nl>
URL: http://www.cs.uu.nl/~piet [PGP]
Private email: P.***********@hccnet.nl

[Josiah Carlson]

Piet van Oostrum wrote:

>>Gerrit Holl <ge****@nl.linux.org> (GH) wrote:
How i could compress string of data?.

>import zlib
>zlib.compress("Hello, world")

GH> 'x\x9c\xf3H\xcd\xc9\xc9\xd7Q(\xcf/\xcaI\x01\x00\x1b\xd4\x04i'

GH> http://www.python.org/doc/current/lib/module-zlib.html

Waw, that compresses it from 12 bytes to 20 bytes :=)

There is no such thing as universal compression - some compressions
result in expansion.

- Josiah

[Terry Reedy]

"Josiah Carlson" <jc******@nospam.uci.edu> wrote in message
news:bv**********@news.service.uci.edu...

Piet van Oostrum wrote:

>>>Gerrit Holl <ge****@nl.linux.org> (GH) wrote:

How i could compress string of data?.

>>import zlib
>>zlib.compress("Hello, world")

GH> 'x\x9c\xf3H\xcd\xc9\xc9\xd7Q(\xcf/\xcaI\x01\x00\x1b\xd4\x04i'

GH> http://www.python.org/doc/current/lib/module-zlib.html

Waw, that compresses it from 12 bytes to 20 bytes :=)

There is no such thing as universal compression

Only if you specify invertibility (losslessness).

f(s) == '' compressess everything except '' itself ;-)

and that len(f(s)) < len(s) for some s and not just <= for all s (which
allows identity 'compression' f(s) == s).
- some compressions result in expansion.

Which is to say that if a 1-1 function maps some strings to smaller
strings, it must correspondingly map others to larger strings. An
interesting CS tidbit that people keep discovering by stumbling over.

Lossless universal expansion is possible: f(s) == ' '+s. But it is into
rather than onto, so only strings starting with ' ' can be inversely
mapped.
Terry J. Reedy

[Josiah Carlson]

Terry Reedy wrote:

"Josiah Carlson" <jc******@nospam.uci.edu> wrote in message
news:bv**********@news.service.uci.edu...

Piet van Oostrum wrote:

>>>>Gerrit Holl <ge****@nl.linux.org> (GH) wrote:
>How i could compress string of data?.
>
>
>>>import zlib
>>>zlib.compress("Hello, world")

GH> 'x\x9c\xf3H\xcd\xc9\xc9\xd7Q(\xcf/\xcaI\x01\x00\x1b\xd4\x04i'

GH> http://www.python.org/doc/current/lib/module-zlib.html

Waw, that compresses it from 12 bytes to 20 bytes :=)

There is no such thing as universal compression

Only if you specify invertibility (losslessness).

f(s) == '' compressess everything except '' itself ;-)

and that len(f(s)) < len(s) for some s and not just <= for all s (which
allows identity 'compression' f(s) == s).

- some compressions result in expansion.

Which is to say that if a 1-1 function maps some strings to smaller
strings, it must correspondingly map others to larger strings. An
interesting CS tidbit that people keep discovering by stumbling over.

Lossless universal expansion is possible: f(s) == ' '+s. But it is into
rather than onto, so only strings starting with ' ' can be inversely
mapped.

Exactly (I was too short on time to say the equivalent this morning, and
even if I had said the equivalent, it likely would not have been as clear).

- Josiah