Destructive hack to delete all transactions in a GNUCash file except those in the target year.

filter_gnucash_transactions.py

#!/usr/bin/env python
"""
Create gnucash file with transactions only in the target year. 
Delete all others.

Requires a gnucash file in sqlite3 format. 
To convert an XML GNUCash file to SQLite3,
"Save As -> Select sqlite3 as the format"

If on Ubuntu the only "Save As" option is XML, try
`sudo apt install libdbd-sqlite3`
Then restart GNUCash and try again.
"""

import datetime
import piecash
import pytz

TZ_MT = pytz.timezone("US/Mountain")
CURRENCY = "USD"


def delete_transactions(gnucash_sql_filename, not_in_year):
    """Delete all transactions not_in_year from gnucash_sql_filename"""

    start = datetime.datetime(not_in_year, 1, 1, 0, 0, 0, 0, TZ_MT)
    finish = datetime.datetime(not_in_year, 12, 31, 23, 59, 59, 99, TZ_MT)

    book = piecash.open_book(gnucash_sql_filename, readonly=False)
    transactions = [x for x in book.transactions if not start <= x.post_date <= finish]

    # piecash uses SQLAlchemy to interact with GNUCash sqlite3 files; hence the
    # `session.delete`. It may be possible to fire off a `DELETE FROM transactions WHERE`
    # but one would want to check piecash's ORM mappings for any required side effects 
    # before trying that.
    session = book.session
    for t in transactions:
        session.delete(t)
    session.commit()
    book.close()


delete_transactions("original-2015-2017-sql.gnucash", 2016)