[Tutor] pickle.dump yielding awkward output

[Dave Angel]

On 02/03/2013 02:26 PM, Spyros Charonis wrote:
> Hello Pythoners,
>
> I am experiencing a strange result with the pickle module when using it to
> write certain results to a separate file.
>
> In short, I have a program that reads a file, finds lines which satisfy
> some criteria, and extracts those lines, storing them in a list. I am
> trying to write this list to a separate file.
>
> The list of extracted lines looks like this:
>
> ATOM      1  N   GLN A   1      29.872  13.384  54.754  1.00 60.40
>    N
>
> ATOM      2  CA  GLN A   1      29.809  11.972  54.274  1.00 58.51
>    C
>
> ATOM      3  C   GLN A   1      28.376  11.536  54.029  1.00 55.13
>    C
>
> The output stored from the call to the pickle.dump method, however, looks
> like this:
>
> (lp0
> S'ATOM      1  N   GLN A   1      29.872  13.384  54.754  1.00 60.40
>      N  \r\n'
> p1
> aS'ATOM      2  CA  GLN A   1      29.809  11.972  54.274  1.00 58.51
>      C  \r\n'
> p2
> aS'ATOM      3  C   GLN A   1      28.376  11.536  54.029  1.00 55.13
>      C  \r\n'
>
> The code I am using to write the output to an external file goes as follows:
>
> def export_antibody_chains():
> ''' EXPORT LIST OF EXTRACTED CHAINS TO FILE '''
> chains_file = open(query + '_Chains', 'wb')
> pickle.dump(ab_chains, chains_file)  # ab_chains is global
> chains_file.close()
> return
>
> Does anyone know why the strings lp0, S', aS' are showing up?
>
>

Pickle stores the type of each variable, as well as the value, and 
stores it in a way as to make it easy to "unpickle" it.

-- 
DaveA