Downloading text files with Python and ftplib.FTP from z/os

Question

I\'m trying to automate downloading of some text files from a z/os PDS, using Python and ftplib.

Since the host files are EBCDIC, I can\'t simply use FTP.retrbinary(

Answer 1

Your writelineswitheol method appends '\r\n' instead of '\n' and then writes the result to a file opened in text mode. The effect, no matter what platform you are running on, will be an unwanted '\r'. Just append '\n' and you will get the appropriate line ending.

Proper error handling should not be relegated to a "bells and whistles" version. You should set up your callback so that your file open() is in a try/except and retains a reference to the output file handle, your write call is in a try/except, and you have a callback_obj.close() method which you use when retrlines() returns to explicitly file_handle.close() (in a try/except) -- that way you get explict error handling e.g. messages "can't (open|write to|close) file X because Y" AND you save having to think about when your files are going to be implicitly closed and whether you risk running out of file handles.

Python 3.x ftplib.FTP.retrlines() should give you str objects which are in effect Unicode strings, and you will need to encode them before you write them -- unless the default encoding is latin1 which would be rather unusual for a Windows box. You should have test files with (1) all possible 256 bytes (2) all bytes that are valid in the expected EBCDIC codepage.

[a few "sanitation" remarks]

1. You should consider upgrading your Python from 3.0 (a "proof of concept" release) to 3.1.

2. To facilitate better understanding of your code, use "i" as an identifier only as a sequence index and only if you irredeemably acquired the habit from FORTRAN 3 or more decades ago :-)

3. Two of the problems discovered so far (appending line terminator to each character, wrong line terminator) would have shown up the first time you tested it.