Managing Personal Finances using Python

Transcript

1. Managing Personal Finances using Python
   Siddhant Goel
    /  @siddhantgoel
   PyMunich May 2019
   

   View Slide

2. Let's start with money.
   

   View Slide

3. 1. What is my net worth?
   

   View Slide

4. 2. What am I spending on?
   

   View Slide

5. 3. How much do I owe others?
   

   View Slide

6. How to debug this?
   

   View Slide

7. duckduckgo.com/?q=personal+ nance+apps
   Mint.com, YNAB, Outbank, Quickbooks, Zuper, GNUCash, ...
   

   View Slide

8. Proprietary
   ... mayyyyybe
   

   View Slide

9. -based
   ... sorry, that's not happening
   

   View Slide

10. Requirements
    Simple
    No cloud
    Ideally free
    Open source
    Hopefully Python
    

    View Slide

11. #plaintextaccounting
    

    View Slide

12. Double Entry Bookkeeping
    

    View Slide

13. beans
    ledger
    hledger
    beancount
    monescript
    

    View Slide

14. $ pip install beancount
    

    View Slide

15. Disclaimers
    I'm not a nancial advisor.
    Aim is to show you what's possible.
    Following slides may or may not contain some maths.
    

    View Slide

16. Accounts
    

    View Slide

17. View Slide

18. Postings & Transactions
    

    View Slide

19. 2019-10-25 "*" "Überweisung BigCorp"
    Assets:DKB 3000.00 EUR
    Income:BigCorp -3000.00 EUR
    

    View Slide

20. ∑(postings) = 0
    

    View Slide

21. View Slide

22. mkdir -p /home/morty/finances
    

    View Slide

23. siddhant@localhost ~/finances % tree .
    .
    ├── config.py
    ├── main.beancount
    ├── originals
    │ └── dkb
    │ └── 2019
    │ ├── credit
    │ │ │── 01-jan.csv
    │ │ └── 02-feb.csv
    │ └── ec
    │ │── 01-jan.csv
    │ └── 02-feb.csv
    ├── poetry.lock
    └── pyproject.toml
    

    View Slide

24. Step 1: Download bank data (CSV)
    

    View Slide

25. Step 2: Convert .csv to .beancount
    

    View Slide

26. Step 3: Append everything to
    main.beancount
    

    View Slide

27. Step 4: Reports!
    

    View Slide

28. bean-check main.beancount
    

    View Slide

29. bean-report main.beancount balances
    siddhant@localhost ~/finances % bean-report main.beancount balances
    Assets:DKB 1450.00 EUR
    Income:BigCorp 3000.00 EUR
    Expenses:Rent -1500.00 EUR
    Expenses:Food 50.00 EUR
    

    View Slide

30. bean-query main.beancount
    SELECT
    month, SUM(position)
    FROM
    year = 2019
    WHERE
    account ~ 'Expenses:Supermarket'
    GROUP BY month
    

    View Slide

31. $ pip install fava
    

    View Slide

32. View Slide

33. View Slide

34. main.beancount
    ; Date format - YYYY-MM-DD
    option "title" "Mustermann"
    option "operating_currency" "EUR"
    2019-10-01 open Assets:DKB
    2019-10-01 open Income:BigCorp
    2019-10-01 open Expenses:Food
    2019-10-01 open Expenses:Rent
    2019-10-25 "*" "Überweisung BigCorp"
    Assets:DKB 3000.00 EUR
    Income:BigCorp -3000.00 EUR
    2019-11-01 "*" "Miete"
    Assets:DKB -1500.00 EUR
    Expenses:Rent 1500.00 EUR
    2019-11-02 "*" "Essen"
    Assets:DKB -50.00 EUR
    Expenses:Food 50.00 EUR
    2019-10-26 balance Assets:DKB 3000.00 EUR
    2019-11-03 balance Expenses:Food 50.00 EUR
    

    View Slide

35. config.py
    from beancount_dkb import ECImporter, CreditImporter
    CONFIG = (
    ECImporter(
    'DE99 9999 9999 9999 9999 99',
    'Assets:DKB',
    'EUR',
    file_encoding='ISO-8859-1',
    ),
    CreditImporter(
    '1234********5678',
    'Assets:DKB',
    'EUR',
    file_encoding='ISO-8859-1',
    ),
    )
    

    View Slide

36. Importers for German banks
    pypi.org/project/beancount-dkb
    pypi.org/project/beancount-ing-diba
    pypi.org/project/beancount-commerzbank
    

    View Slide

37. Sample Importer
    from beancount.core.amount import Amount
    from beancount.core.number import Number
    from beancount.ingest.importer import ImporterProtocol
    class SampleImporter(ImporterProtocol):
    # ...
    def identify(self, file_):
    """Check if file_ is from the bank we're supposed to work with
    """
    # ...
    def extract(self, file_):
    """Read file_, and emit a list of beancount data structures
    """
    

    View Slide

38. Budgeting
    2012-01-01 custom "budget" Expenses:Coffee "daily" 4.00 EUR
    2013-01-01 custom "budget" Expenses:Books "weekly" 20.00 EUR
    2014-02-10 custom "budget" Expenses:Groceries "monthly" 40.00 EUR
    2015-05-01 custom "budget" Expenses:Electricity "quarterly" 85.00 EUR
    2016-06-01 custom "budget" Expenses:Holiday "yearly" 2500.00 EUR
    

    View Slide

39. Resources
    https://plaintextaccounting.org
    https://www.reddit.com/r/plaintextaccounting
    https://awesome-beancount.com/
    https://aumayr.github.io/beancount-docs-static/
    https://beancount.github.io/fava/
    Slides
    https://bit.ly/sg-pymunich-2019
    

    View Slide

40. Thanks for your time!
    bit.ly/sg-pymunich-2019
     /  @siddhantgoel
     sgoel.org
    

    View Slide