3. The stingray Package

The stingray package implements a Schema-based File Reader. This allows us to use flat-file and workbook data from Python without having to clone an application for each physical file format or logical layout.

It also allows us to use semi-structured data like JSON, YAML or an outline. This can be handled consistently with structured data.

This package includes

• A definition for “workbook”, “sheet” and “cell”. This can subsume csv, xlrd as well as XML parsers for XLSX and ODS files. This makes the physical format transparent to an application.
• A definition for a schema. Not a complex XSD, but the limited, flat schema appropriate for rows in sheets of a workbook in approximately First Normal Form. This is extended to handle the simple hierarcical COBOL features.
• Classes to load a schema that’s embedded either in a sheet or in a separate file.
• A COBOL schema loader as an extension to the default loaders.

This depends on Python 3.3.

The structure of the stingray package is as follows.

• __init__.py. Some essential overhead. See stingray __init__.py.
• cell.py. Cell Module – Data Element Containers and Conversions defines the Cell class hierarchy. Imported as stingray.cell.
• sheet.py. Sheet Module – Sheet and Row Access defines the Sheet class hierarchy that supports sheets with embedded as well as external schema. Imported as stingray.sheet.
• workbook.py. The Workbook Package – Uniform Wrappers for Workbooks families. Imported as stingray.workbook.
• schema. This package defines a schema and schema loaders.
  • __init__.py. Schema Package – Schema and Attribute Definitions. Imported as stingray.schema. This is the generic, flat schema and superclasses for the more complex COBOL schema.
  • loader.py. Schema Loader Module – Load Embedded or External Schema. A loader for the generic, flat schema. Imported as stingray.schema.loader. Applications will often extend schema loaders to handle peculiar formats or multi-line headings or other workbook formatting.
• cobol. This package extends a schema and schema loaders to handle COBOL files.
  • __init__.py. The COBOL Package. Imported as stingray.cobol. These are extensions to stingray.cell, stingray.sheet and stingray.workbook.
  • loader.py COBOL Loader Module – Parse COBOL Source to Load a Schema. A loader for COBOL-syntax schema. Imported as stingray.cobol.loader.
  • defs.py. COBOL Definitions Module – Handle COBOL DDE’s. Base definitions used by both __init__.py and loader.py.
• snappy. This module is a minimal implementation of a reader for files written with Snappy compression.
• protobuf. This module is a minimal implementation of a reader for objects represented using protobuf.