tableio-cfg-json 0.4

config-as-json configuration encapsulation for tableio.

tableio-cfg-json

tableio-cfg-json stores TableIO configuration as validated JSON by using config-as-json.

Use it when an application uses TableIO for table-like files and wants persistent, user-editable configuration for formats, implementations and format-specific options. The configuration objects are both TableIO ConfigData objects and config-as-json Config objects, so the same object can be written as configuration file (as JSON), read back later, validated, and passed to TableIO.

Is this package for you?

This package is a good fit when one or more of these apply:

• Your application uses TableIO.
• You already use config-as-json, or can accept using it for persistent configuration.
• You want one configuration file to describe one TableIO input or output endpoint.
• You want to nest one or more TableIO endpoint configurations inside a larger application configuration file.
• You want validation and generated user documentation for the TableIO options that are relevant to your application's capabilities.

This package is probably not the right one when:

• You are looking for the table reader or writer itself. Use TableIO directly.
• Your program always uses one hard-coded table format and has no persistent configuration.
• You do not want to use config-as-json for configuration files.

Installation

tableio-cfg-json requires Python 3.12 or newer.

pip install --upgrade tableio-cfg-json

Quick start

Create a compact JSON configuration file for one TableIO endpoint:

from pathlib import Path
import sys

from tableio import FileAccess, access_capabilities
from tableio_cfg_json import tio_json_config_default

config_file = Path('tableio.cfg')
file_access = FileAccess.CREATE
capabilities = access_capabilities(file_access, error_file=sys.stderr)
config = tio_json_config_default(capabilities=capabilities,
                                 file_access=file_access,
                                 format_name='CSV')
config.write(to_json_filename=config_file)

For CSV this writes a small file like:

{
    "format_name": "CSV"
}

Read the configuration back and use it with TableIO:

from pathlib import Path
import sys

from tableio import FileAccess, access_capabilities, tio_config_create
from tableio_cfg_json import TioJsonConfig

config_file = Path('tableio.cfg')
table_file = Path('capitals.csv')
file_access = FileAccess.CREATE
capabilities = access_capabilities(file_access, error_file=sys.stderr)
config = TioJsonConfig(capabilities=capabilities,
                       file_access=file_access,
                       from_json_filename=config_file)
with tio_config_create(config=config, file_name=table_file,
                       file_access=file_access,
                       capabilities=capabilities) as table_io:
    table_io.write_table_listdata([
        ['Capital', 'Country'],
        ['Copenhagen', 'Denmark']
    ])

If implementation is omitted, TableIO chooses a matching implementation at runtime. If the user wants to lock down a specific implementation, it can be stored explicitly in JSON.

Optional settings can be added at the top level or in format-specific nested sections such as csv, html and latex. Compact output omits unset optional values, while template-style output can include all current default options.

Please see the teaching examples for a more thorough introduction.

Main entry points

• TioJsonConfig Complete JSON-backed TableIO configuration for one endpoint. It can read JSON, write JSON and be passed to TableIO as normal configuration data.

• tio_config_create() create a TableIO object from a TioJsonConfig object.

Helpers and details

• tio_json_config_default() Create a validated default TioJsonConfig using TableIO's recommended choices for the requested capabilities and file access.

• TioJsonCsvConfig, TioJsonHtmlConfig, TioJsonLatexConfig Optional nested configuration sections for format-specific settings.

• describe_config(), describe_config_members(), describe_config_reference(), describe_config_example(), get_config_member_names() and get_general_cfg_info() Helpers for generating plain text syntax guides for configuration files.

• tio_json_config_wizard() Interactive helper for creating one TableIO endpoint configuration through a user interface bridge.

• WizardUiBridge and WizardUiBridgeConsole Interfaces for connecting the wizard to a console, GUI or scripted UI.

Validation model

The configuration file (in JSON) stores durable TableIO choices such as format_name, implementation, character encoding, presentation options and format-specific settings. Runtime values such as the actual file name are not stored in this configuration.

Validation happens in two layers:

• config-as-json validates JSON structure, member names and member value types.
• TableIO validates whether the selected format, implementation, capabilities and file access can work together.

Choice values are matched case-insensitively where TableIO defines a finite set of choices. For example, configuration file may use excel and the config object will store TableIO's normal Excel spelling after validation.

Nested application configs

TioJsonConfig can be used as the whole configuration file for a small program, or as a nested member inside a larger config-as-json application configuration. This is useful when one application has several TableIO endpoints, for example one input table and two independently configured output tables.

For larger configs, create each nested TioJsonConfig with the capabilities and file access for that endpoint. A read endpoint and a create endpoint may need different defaults and may validate different implementations.

The teaching examples show both styles.

Documentation

• Teaching examples and walkthroughs: example/src/example/README.md

• Public API notes: doc/api.md

• Protected/internal API notes: doc/protected_api.md

• Source repository: tableio_cfg_json

License

MIT

Test summary

• Test result: 380 passed in 14s
• No flake8 warnings.
• No mypy errors found.
• No python layout warnings.
• Built version(s): 0.4
• Build and test using Python 3.14.5