Hi All,

The latest entries into http://python.faqts.com

regards,

Fiona Czuczman

Including:

- Manipulating PNG files using Win32 PIL
- How can I map the read() function of a file object?
- What is the fastest way to search a binary file for a certain byte
pattern (**** in my case)?
- Embedding Python code in a C++ program, I get dynamic linking errors
if I try to import any non-built in module, what's wrong?

## New Entries #################################################

-------------------------------------------------------------
Manipulating PNG files using Win32 PIL
http://www.faqts.com/knowledge-base/view.phtml/aid/5025
-------------------------------------------------------------
Fiona Czuczman
Olivier A. Dagenais

Problem:

I've writen a script to generate PNG images using PIL.  It works a treat
under Linux, but when I try to port it to MSWindows, the
PIL/PngImagePlugin spits saying that I don't have a zip encoder. I
already have a copy of pkzip, but I got hold of a copy of gzip.exe and
stuck it in C:\Windows\zip.exe but to no avail. Can anyone confirm that
I need a zip executable, or is the PIL wanting a DLL, etc?

Solution:

http://www.pythonware.com/downloads.htm

Says this, near the end of the page:

"Optional support libraries must be downloaded separately: jpeg and
zlib."

...you'll want to follow the zlib link:

ftp://ftp.freesoftware.com/.0/infozip/zlib/zlib.html

The zlib library is used for manipulating PNG files...

-------------------------------------------------------------
How can I map the read() function of a file object?
http://www.faqts.com/knowledge-base/view.phtml/aid/5028
-------------------------------------------------------------
Fiona Czuczman
Peter Schneider-Kamp, Bjorn Pettersen

Just use a lambda like this:

map(lambda f:open(f,"r").read(), list_of_filenames)

or perhaps:

  def openAndRead(filename):
      return open(filename).read()

  map( openAndRead, listOfFilenames )

-------------------------------------------------------------
What is the fastest way to search a binary file for a certain byte pattern (**** in my case)?
http://www.faqts.com/knowledge-base/view.phtml/aid/5029
-------------------------------------------------------------
Fiona Czuczman
Bjorn Pettersen

Use:

import string
string.find( open('my_binary_file','rb').read(), '****' )

-------------------------------------------------------------
Embedding Python code in a C++ program, I get dynamic linking errors if I try to import any non-built in module, what's wrong?
http://www.faqts.com/knowledge-base/view.phtml/aid/5030
-------------------------------------------------------------
Fiona Czuczman
Ted Drain

Problem:

I am trying to learn how to embed Python code in a C++ program. I got
the example from the docs (the one that imports sys and prints out a
couple of strings -- search from initxyzzy in google). The problem I get
is that if I try to import any non-built in module, I get dynamic
linking errors. For example, adding the following line 31 works:

_______________________________________________________________________
...
     29         /* Execute some Python statements (in module __main__)
*/
     30         PyRun_SimpleString("import sys\n");
-->  31         PyRun_SimpleString("import thread\n");
     32         PyRun_SimpleString("print sys.builtin_module_names\n");
...
_______________________________________________________________________

but adding the following line instead:

_______________________________________________________________________
...
     29         /* Execute some Python statements (in module __main__)
*/
     30         PyRun_SimpleString("import sys\n");
-->  31         PyRun_SimpleString("import random\n");
     32         PyRun_SimpleString("print sys.builtin_module_names\n");
...
_______________________________________________________________________

produces:

_______________________________________________________________________
[lopes@groucho lopes]$ ./demo
Hello, brave new world

Traceback (innermost last):
  File "<string>", line 1, in ?
  File "/usr/lib/python1.5/random.py", line 22, in ?
    import whrandom
  File "/usr/lib/python1.5/whrandom.py", line 140, in ?
    _inst = whrandom()
  File "/usr/lib/python1.5/whrandom.py", line 46, in __init__
    self.seed(x, y, z)
  File "/usr/lib/python1.5/whrandom.py", line 58, in seed
    import time
ImportError: /usr/lib/python1.5/lib-dynload/timemodule.so: undefined
symbol: PyExc_IOError
('__builtin__', '__main__', 'imp', 'marshal', 'pcre', 'posix', 'regex',
'signal', 'sys', 'thread')
['xyzzy', 'os.path', 'os', 'exceptions', '__main__', 'posix',
'whrandom', 'sys', '__builtin__', 'site', 'random', 'signal',
'UserDict', 'posixpath', 'stat']
./demo
['./demo']
_______________________________________________________________________

Solution:

If you're building w/ gcc, add the link line option:

-Wl,-E