Extending jrnl

jrnl can be extended with custom importers and exporters.

Note that custom importers and exporters can be given the same name as a built-in importer or exporter to override it.

Custom Importers and Exporters are traditional Python packages, and are installed (into jrnl) simply by installing them so they are available to the Python interpreter that is running jrnl.

Entry Class

Both the Importers and the Exporters work on the Entry class. Below is a (selective) description of the class, it's properties and functions:

Entry (class) at jrnl.Entry.Entry.
- title (string): a single line that represents a entry's title.
- date (datetime.datetime): the date and time assigned to an entry.
- body (string): the main body of the entry. Can be basically any length. jrnl assumes no particular structure here.
- starred (boolean): is an entry starred? Presumably, starred entries are of particular importance.
- tags (list of strings): the tags attached to an entry. Each tag includes the pre-facing "tag symbol".
- __init__(journal, date=None, text="", starred=False): contractor method
  - journal (jrnl.Journal.Journal): a link to an existing Journal class. Mainly used to access it's configuration.
  - date (datetime.datetime)
  - text (string): assumed to include both the title and the body. When the title, body, or tags of an entry are requested, this text will the parsed to determine the tree.
  - starred (boolean)

Entries also have "advanced" metadata if they are using the DayOne backend, but we'll ignore that for the purposes of this demo.

Custom Importer

If you have a (custom) datasource that you want to import into your jrnl (perhaps like a blog export), you can write a custom importer to do this.

An importer takes the source data, turns it into Entries and then appends those entries to a Journal. Here is a basic Importer, assumed to be provided with a nicely formated JSON file:

# pelican\contrib\importer\sample_json.py
import sys

from jrnl import Entry
from jrnl.plugins.base import BaseImporter

__version__ = "1.0.0"

class Importer:
    """JSON Importer for jrnl."""

    names = ["json"]
    version = __version__

    @staticmethod
    def import_(journal, input=None)
        """
        Given a nicely formatted JSON file, will add the
        contained Entries to the journal.
        """
        
        old_count = len(journal.entries)
        if input:
            with open(input, "r", encoding="utf-8") as f:
                data = json.loads(f)
        else:
            try:
                data = sys.stdin.read()
            except KeyboardInterrupt:
                print(
                    "[Entries NOT imported into journal.]",
                    file=sys.stderr,
                )
                sys.exit(0)

        for json_entry in data:
            raw = json_entry["title"] + "/n" + json_entry["body"]
            date = json_entry["date"]
            entry = Entry.Entry(self, date, raw)
            journal.entries.append(entry)

        new_cnt = len(journal.entries)
        print(
            "[{} entries imported to '{}' journal]".format(
                new_cnt - old_cnt, journal.name
            ),
            file=sys.stderr,
        )

Note that the above is very minimal, doesn't do any error checking, and doesn't try to import all possible entry metadata.

Some implementation notes:

The importer class must be named Importer, and should sub-class jrnl.plugins.base.BaseImporter.
The importer module must be within the jrnl.contrib.importer namespace.
The importer must not have any __init__.py files in the base directories.
The importer must be installed as a Python package available to the same Python interpreter running jrnl.
The importer must expose at least the following the following members:
- version (string): the version of the plugin. Displayed to help the user debug their installations.
- names (list of strings): these are the "names" that can be passed to the CLI to invole your importer. If you specify one used by a built-in plugin, it will overwrite it (effectively making the built-in one unavailable).
- import_(journal, input=None): the actual importer. Must append entries to the journal passed to it. It is recommended to accept either a filename or standard input as a source.

Custom Exporter

Custom exporters are useful to make jrnl's data available to other programs. One common usecase would to generate the input to be used by a static site generator or blogging engine.

An exporter take either a whole journal or a specific entry and exports it. Below is a basic JSON Exporter; note that a more extensive JSON exporter is included in jrnl and so this (if installed) would override the built in exporter.

# pelican\contrib\exporter\custom_json.py
import json

from jrnl.plugins.base import BaseExporter

__version__ = "1.0.0"

class Exporter(BaseExporter):
    """
    This basic Exporter can convert entries and journals into JSON.
    """

    names = ["json"]
    extension = "json"
    version = __version__

    @classmethod
    def entry_to_dict(cls, entry):
        return = {
            "title": entry.title,
            "body": entry.body,
            "date": entry.date.strftime("%Y-%m-%d"),
        }

    @classmethod
    def export_entry(cls, entry):
        """Returns a json representation of a single entry."""
        return json.dumps(cls.entry_to_dict(entry), indent=2) + "\n"

    @classmethod
    def export_journal(cls, journal):
        """Returns a json representation of an entire journal."""
        tags = get_tags_count(journal)
        result = {
            "entries": [
                cls.entry_to_dict(e) for e in journal.entries
            ],
        }
        return json.dumps(result, indent=2)

Note that the above is very minimal, doesn't do any error checking, and doesn't export all entry metadata.

Some implementation notes:

the exporter class must be named Exporter and should sub-class jrnl.plugins.base.BaseExporter.
the exporter module must be within the jrnl.contrib.exporter namespace.
The exporter must not have any __init__.py files in the base directories.
The exporter must be installed as a Python package available to the same Python interpreter running jrnl.
the exporter should expose at least the following the following members (there are a few more you will need to define if you don't subclass jrnl.plugins.base.BaseExporter):
- version (string): the version of the plugin. Displayed to help the user debug their installations.
- names (list of strings): these are the "names" that can be passed to the CLI to invole your exporter. If you specific one used by a built-in plugin, it will overwrite it (effectively making the built-in one unavailable).
- extension (string): the file extention used on exported entries.
- export_entry(entry): given an entry, returns a string of the formatted, exported entry.
- export_journal(journal): given a journal, returns a string of the formatted, exported entries of the journal.

Development Tips

editable installs (pip install -e ...) don't seem to play nice with the namespace layout. If your plugin isn't appearing, try a non-editable install of both jrnl and your plugin.

7.6 KiB Raw Blame History

Extending jrnl

Entry Class

Custom Importer

Custom Exporter

Development Tips

7.6 KiB

Raw Blame History