example.beancount

2024-01-01 open Assets:Checking
2024-01-01 open Expenses:Groceries

2024-01-01 * "Groceries"
  Expenses:Groceries 10 USD
  Assets:Checking

postingtype.py

from decimal import Decimal
from io import StringIO
from typing import Sequence

from beancount.core.amount import Amount
from beancount.core.data import Posting, Transaction
from beancount.loader import load_file
from beancount.parser.printer import print_entries

# This has the type error with pyright-1.1.363:
#
#   postingtype.py:12:11 - error: Argument of type "None" cannot be assigned to parameter "units" of type "Amount" in function "__new__"
#     "None" is incompatible with "Amount" (reportArgumentType)
#
# But it's not a runtime error.
p = Posting(
    account="Expenses:Groceries",
    units=None,
    cost=None,
    price=None,
    flag=None,
    meta=None,
)

entries, errors, options = load_file('example.beancount')
assert not errors
transaction = entries[2]
checking_posting = transaction.postings[1]

# The text of this transaction in the ledger is:
#
#     2024-01-01 * "Groceries"
#       Expenses:Groceries 10 USD
#       Assets:Checking
#
# But Beancount's load_file adds the -10 USD to it.
assert checking_posting.account == 'Assets:Checking'
assert checking_posting.units == Amount(Decimal(-10), 'USD')

def entries_to_string(entries: Sequence[Transaction]):
  output = StringIO()
  print_entries(entries, file=output)
  output.seek(0)
  return output.read()

# This prints the amount that the Beancount importer added:
#
#     2024-01-01 * "Groceries"
#       Expenses:Groceries   10 USD
#       Assets:Checking     -10 USD
#
print(entries_to_string(entries))