COBOL Copybook parser in Python

This is a COBOL Copybook parser in Python featuring the following options:

• Parse the Copybook into a usable format to use in Python
• Clean up the Copybook by processing REDEFINES statements and remove unused definitions
• Denormalize the Copybook
• Write the cleaned Copybook in COBOL
• Strip prefixes of field names and ensure that the Copybook only contains unique names
• Can be used from the command-line or included in own Python projects

Because I couldn't find a COBOL Copybook parser that fitted all my needs I wrote my own. It doesn't support all functions found in the Copybook, just the ones that I met on my path: REDEFINES, INDEXED BY, OCCURS.

On a day to day basis I use it so that Informatica PowerCenter creates only 1 table of my COBOL data instead multiple.

The code uses the pic parser code from pyCOBOL.

This code is licensed under GPLv3.

Installation

The easiest way to install python-cobol is using pip:

$ pip install python-cobol

Example output

Below is an example Copybook file before and after being processed.

Before:

00000* Example COBOL Copybook file AAAAAAAA
0000001 PAULUS-EXAMPLE-GROUP. AAAAAAAA
0000005 PAULUS-ANOTHER-GROUP OCCURS0003TIMES. AAAAAAAA
0000010 PAULUS-FIELD-1 PIC X(3). AAAAAAAA
0000010 PAULUS-FIELD-2 REDEFINES PAULUS-FIELD-1 PIC 9(3). AAAAAAAA
0000010 PAULUS-FIELD-3 OCCURS0002TIMES AAAAAAAA
00000PIC S9(3)V99. AAAAAAAA
0000005 PAULUS-THIS-IS-ANOTHER-GROUP. AAAAAAAA
0000010 PAULUS-YES PIC X(5). AAAAAAAA

After:

01 EXAMPLE-GROUP. 05 FIELD-2-1 PIC 9(3). 05 FIELD-3-1-1 PIC S9(3)V99.05 FIELD-3-1-2 PIC S9(3)V99.05 FIELD-2-2 PIC 9(3). 05 FIELD-3-2-1 PIC S9(3)V99.05 FIELD-3-2-2 PIC S9(3)V99.05 FIELD-2-3 PIC 9(3). 05 FIELD-3-3-1 PIC S9(3)V99.05 FIELD-3-3-2 PIC S9(3)V99.05 THIS-IS-ANOTHER-GROUP. 10 YES PIC X(5). 

How to use

You can use it in two ways: inside your own python code or as a stand-alone command-line utility.

Command-line

Do a git clone from the repository and inside your brand new python-cobol folder run:

$ python cobol.py example.cbl

This will process the redefines, denormalize the file, strip the prefixes and ensure all names are unique.

The utility allows for some command-line switches to disable some processing steps.

	$ python cobol.py --help
usage: cobol.py [-h] [--skip-all-processing] [--skip-unique-names]
[--skip-denormalize] [--skip-strip-prefix]
filename
Parse COBOL Copybooks
positional arguments:
filename The filename of the copybook.
optional arguments:
-h, --help show this help message and exit
--skip-all-processing
Skips unique names, denormalization and .
--skip-unique-names Skips making all names unique.
--skip-denormalize Skips denormalizing the COBOL.
--skip-strip-prefix Skips stripping the prefix from the names.	

From within your Python code

The parser can also be called from your Python code. All you need is a list of lines in COBOL Copybook format. See example.py how one would do it:

importcobolwithopen("example.cbl",'r') asf:
forrowincobol.process_cobol(f.readlines()):
printrow['name']

It is also possible to call one of the more specialized functions within cobol.py:

• clean_cobol(lines)

  Cleans the COBOL by converting the cobol informaton to single lines

• parse_cobol(lines)

  Parses a list of COBOL field definitions into a list of dictionaries containing the parsed information.

• denormalize_cobol(lines)

  Denormalizes parsed COBOL lines

• clean_names(lines, ensure_unique_names=False, strip_prefix=False, make_database_safe=False)

  Cleans names of the fields in a list of parsed COBOL lines. Options to strip prefixes, enforce unique names and make the names database safe by converting dashes (-) to underscores (_)

• print_cobol(lines)

  Prints parsed COBOL lines in the Copybook format