Comunicate with external programs via popen

[solarw]

OS linux 2.6.18
python 2.4.3

i tried to compress data throw gzip using popen2.popen3

import  popen2
a=popen2.Popen3("gzip -f")
a.tochild.write("test data")
a.tochild.flush()
a.fromchild.read(5) #try to read 5 bytes from gzip
 

but can't recive thouse 5 bytes, program hangs on read
cat /filename |gzip -f>filename2 - works excelent
don't offer to use zlib or bz2 modules
i wish to compress long data sequens throw external program so sending EOF is not good decition

how to write data to external program and recive result immidiatly?

[kudos]

Im just curious, are you able to send a EOF (Ctrl-D) to gzip before it returns?
-kudos

OS linux 2.6.18
python 2.4.3

i tried to compress data throw gzip using popen2.popen3

import  popen2
a=popen2.Popen3("gzip -f")
a.tochild.write("test data")
a.tochild.flush()
a.fromchild.read(5) #try to read 5 bytes from gzip
 

but can't recive thouse 5 bytes, program hangs on read
cat /filename |gzip -f>filename2 - works excelent
don't offer to use zlib or bz2 modules
i wish to compress long data sequens throw external program so sending EOF is not good decition

how to write data to external program and recive result immidiatly?

[solarw]

Im just curious, are you able to send a EOF (Ctrl-D) to gzip before it returns?
-kudos

i need to proceed data strem so if i send EOF stream will be interupted

[bartonc]

I'm on Windows, so can't be of much help. But reading the docs, your usage of the class appears to be a bit off:

popen3( cmd[, bufsize[, mode]])
Executes cmd as a sub-process. Returns the file objects (child_stdout, child_stdin, child_stderr).
On Unix, a class defining the objects returned by the factory functions is also available.

class Popen3( cmd[, capturestderr[, bufsize]])
This class represents a child process.

Normally, Popen3 instances are created using the popen2() and popen3() factory functions described above.

6.9.2 address flow issues. I hope this is of some use,
Barton

[kudos]

i need to proceed data strem so if i send EOF stream will be interupted

yes I know, but are you able to send something to the gzip program at all? I thought that the program had to return before python could manipulate it (correct me if I am wrong here )

By the way, why not just use zlib modules that comes with python? I think there even is a gzip module too (If I remeber correctly the zlib and gzip are equal apart from the header format).

-kudos

[solarw]

yes I know, but are you able to send something to the gzip program at all? I thought that the program had to return before python could manipulate it (correct me if I am wrong here )

By the way, why not just use zlib modules that comes with python? I think there even is a gzip module too (If I remeber correctly the zlib and gzip are equal apart from the header format).

-kudos

i wish to compress data stream by lzma program
pylzma is not ready for this, so i decide to use external lzma program
problem with lzma is like problem with gzip