beancount-importer-rules 0.1.2

Beancount importer rules engine

beancount-import-rules

beancount-import-rules is a simple, declarative, smart, and easy-to-use library for importing extracted transactions.

It generates Beancount transactions based on predefined rules.

Install

pip install beancount-import-rules

or

pdm install beancount-import-rules

or

poetry add beancount-import-rules

Usage

1. create a import.yml file.
2. define your import rules in the file; see below for the schema
   1. to the top of your rules file, add # yaml-language-server: $schema=https://raw.githubusercontent.com/zenobi-us/beancount-importer-rules/master/schema.json for schema hints.
3. run beancount-import import to import transactions

Example

import.yaml.

# yaml-language-server: $schema=https://raw.githubusercontent.com/zenobi-us/beancount-importer-rules/master/schema.json

# the `context` defines global variables to be referenced in the Jinja2 template for
# generating transactions
context:
  routine_expenses:
    "Amazon Web Services":
      account: Expenses:Engineering:Servers:AWS
    Netlify:
      account: Expenses:Engineering:ServiceSubscription
    Mailchimp:
      account: Expenses:Marketing:ServiceSubscription
    Circleci:
      account: Expenses:Engineering:ServiceSubscription
    Adobe:
      account: Expenses:Design:ServiceSubscription
    Digital Ocean:
      account: Expenses:Engineering:ServiceSubscription
    Microsoft:
      account: Expenses:Office:Supplies:SoftwareAsService
      narration: "Microsoft 365 Apps for Business Subscription"
    Mercury IO Cashback:
      account: Expenses:CreditCardCashback
      narration: "Mercury IO Cashback"
    WeWork:
      account: Expenses:Office
      narration: "Virtual mailing address service fee from WeWork"

# the `inputs` defines which files to import, what type of extractor to use,
# and other configurations, such as `prepend_postings` or default values for generating
# a transaction
inputs:
  - match: "import-data/mercury/*.csv"
    config:
      # use `mercury` extractor for extracting transactions from the input file
      extractor: beanhub_extract.extractors.mercury:MercuryExtractor
      # the default output file to use
      default_file: "books/{{ date.year }}.bean"
      # postings to prepend for all transactions generated from this input file
      prepend_postings:
        - account: Assets:Bank:US:Mercury
          amount:
            number: "{{ amount }}"
            currency: "{{ currency | default('USD', true) }}"

# the `imports` defines the rules to match transactions extracted from the input files and
# how to generate the transaction
imports:
  - name: Routine expenses
    match:
      extractor:
        equals: "mercury"
      desc:
        one_of:
          - Amazon Web Services
          - Netlify
          - Mailchimp
          - Circleci
          - WeWork
          - Adobe
          - Digital Ocean
          - Microsoft
          - Mercury IO Cashback
    actions:
      # generate a transaction into the beancount file
      - file: "books/{{ date.year }}.bean"
        txn:
          narration: "{{ routine_expenses[desc].narration | default(desc, true) | default(bank_desc, true) }}"
          postings:
            - account: "{{ routine_expenses[desc].account }}"
              amount:
                number: "{{ -amount }}"
                currency: "{{ currency | default('USD', true) }}"

  # To avoid many match/actions statements for mostly identical transaction template,
  # you can also define different match conditions and the corresponding variables for the transaction template
  - name: Routine Wells Fargo expenses
    # the condition shared but all the matches
    common_cond:
      extractor:
        equals: "plaid"
      file:
        suffix: "(.+)/Wells Fargo/(.+).csv"
    match:
      - cond:
          desc: "Comcast"
        vars:
          account: Expenses:Internet:Comcast
          narration: "Comcast internet fee"
      - cond:
          desc: "PG&E"
        vars:
          account: Expenses:Gas:PGE
          narration: "PG&E Gas"
    actions:
      # generate a transaction into the beancount file
      - file: "books/{{ date.year }}.bean"
        txn:
          payee: "{{ payee | default(omit, true) }}"
          narration: "{{ narration | default(desc, true) | default(bank_desc, true) }}"
          postings:
            - account: "{{ account }}"
              amount:
                number: "{{ -amount }}"
                currency: "{{ currency | default('USD', true) }}"

  - name: Receive payments from contracting client
    match:
      extractor:
        equals: "mercury"
      desc:
        equals: Evil Corp
    actions:
      - txn:
          narration: "Receive payment from Evil Corp"
          postings:
            - account: "Assets:AccountsReceivable:EvilCorpContracting"
              amount:
                number: "{{ -amount / 300 }}"
                currency: "EVIL.WORK_HOUR"
              price:
                number: "300.0"
                currency: "USD"

  - name: Ignore unused entries
    match:
      extractor:
        equals: "mercury"
      desc:
        one_of:
        - Mercury Credit
        - Mercury Checking xx1234
    actions:
      # ignore action is a special type of import rule action to tell the importer to ignore the
      # transaction so that it won't show up in the "unprocessed" section in the import result
      - type: ignore

Then, run the following command to import the transactions:

beancount-import import

Scheme definition

Import Doc

The import file should be located at .beanhub/imports.yaml. It has the following keys:

• context: a dictionary for global variable definitions to be referenced in all Jinja2 - template rendering and transaction generation, as described in the - Context Definition section.
• inputs: Define which CSV files to import and their corresponding configurations, as described in the Input Definition section
• imports: Define rules for which raw transactions to match and what to do with them. As described in the Import Definition section, new transactions will usually be generated based on the provided templates.
• outputs: Define configurations for output files, currently not implemented yet

Context Definition

Context comes in handy when you need to define variables to be referenced in the template. As you can see in the example, we define a routine_expenses dictionary variable in the context.

context:
  routine_expenses:
    "Amazon Web Services":
      account: Expenses:Engineering:Servers:AWS
    Netlify:
      account: Expenses:Engineering:ServiceSubscription
    Mailchimp:
      account: Expenses:Marketing:ServiceSubscription
    Circleci:
      account: Expenses:Engineering:ServiceSubscription
    Adobe:
      account: Expenses:Design:ServiceSubscription
    Digital Ocean:
      account: Expenses:Engineering:ServiceSubscription
    Microsoft:
      account: Expenses:Office:Supplies:SoftwareAsService
      narration: "Microsoft 365 Apps for Business Subscription"
    Mercury IO Cashback:
      account: Expenses:CreditCardCashback
      narration: "Mercury IO Cashback"
    WeWork:
      account: Expenses:Office
      narration: "Virtual mailing address service fee from WeWork"

Then, in the transaction template, we look up the dictionary to find out what narration value to use:

"{{ routine_expenses[desc].narration | default(desc, true) | default(bank_desc, true) }}"

Input Definition

Input definition comes with two keys:

• match: Rule for matching CSV files. Currently, only the Simple File Match rule is supported. Please see the Simple File Match Definition section for more details.
• config: The configuration of the matched input CSV files. Please see the Input Config Definition section.

Simple File Match Definition

Currently, we support three different modes of matching a CSV file. The first one is the default one, glob. A simple string would make it use glob mode like this:

inputs:
  - match: "import-data/mercury/*.csv"

You can also do an exact match like this:

inputs:
- match:
    equals: "import-data/mercury/2024.csv"

Or, if you prefer regular expression:

inputs:
- match:
    regex: "import-data/mercury/2([0-9]+).csv"

Input Config Definition

The following keys are available for the input configuration:

• extractor: A python import path to the extractor to use for extracting transactions from the matched file. The format is package.module:extractor_class. For example, beancount_import_rules.extractors.plaid:PlaidExtractor. Your Extractor Class should inherit from beancount_import_rules.extractors.ExtractorBase or beancount_import_rules.extractors.ExtractorCsvBase.

• default_file: The default output file for generated transactions from the matched file to use if not specified in the add_txn action.

• prepend_postings: Postings are to be prepended for the generated transactions from the matched file. A list of posting templates as described in the Add Transaction Action section.

• append_postings: Postings are to be appended to the generated transactions from the matched file. A list of posting templates as described in the Add Transaction Action section.

• default_txn: The default transaction template values to use in the generated transactions from the matched file. Please see the Add Transaction Action section.

Import Config Definition

The following keys are available for the import configuration:

• name: An optional name for the user to comment on this matching rule. Currently, it has no functional purpose.
• match: The rule for matching raw transactions extracted from the input CSV files. As described in the Import Match Rule Definition
• actions: Decide what to do with the matched raw transactions, as the Import Action Definition describes.

Import Match Rule Definition

The raw transactions extracted by the extractor come with many attributes. Here we list only a few from it:

• extractor: Name of the extractor
• file: The CSV file path
• lineno: The row line number
• date: Date of the transaction
• desc: Description of the transaction
• bank_desc: Exact description of the transaction from the bank
• amount: Transaction amount
• currency: Currency of the transaction

For the complete list of available raw transaction attributes, please read the beancount-importer-rules source code to learn more.

The match object should be a dictionary. The key is the transaction attribute to match, and the value is the regular expression of the target pattern to match. All listed attributes need to match so that a transaction will considered matched. Only simple matching logic is possible with the current approach. We will extend the matching rule to support more complex matching logic in the future, such as NOT, AND, OR operators. The following matching modes for the transaction value are available.

Regular expression

When a simple string value is provided, regular expression matching will be used. Here's an example:

imports:
  - match:
      desc: "^DoorDash (.+)"

Exact match

To match an exact value, one can do this:

imports:
- match:
    desc:
      equals: "DoorDash"

Prefix match

To match values with a prefix, one can do this:

imports:
- match:
    desc:
      prefix: "DoorDash"

Suffix match

To match values with a suffix, one can do this:

imports:
- match:
    desc:
      suffix: "DoorDash"

Contains match

To match values containing a string, one can do this:

imports:
- match:
    desc:
      contains: "DoorDash"

One of match

To match values belonging to a list of values, one can do this:

imports:
- match:
    desc:
      one_of:
        - DoorDash
        - UberEats
        - Postmate

Match with variables

From time to time, you may find yourself writing similar import-matching rules with similar transaction templates. To avoid repeating yourself, you can also write multiple match conditions with their corresponding variables to be used by the template in the same import statement. For example, you can simply do the following two import statements:

imports:
  - name: PG&E Gas
    match:
      extractor:
        equals: "plaid"
      desc:
        prefix: "PGANDE WEB ONLINE "
    actions:
      - txn:
          payee: "{{ payee }}"
          narration: "Paid American Express Blue Cash Everyday"
          postings:
            - account: "Expenses:Util:Gas:PGE"
              amount:
                number: "{{ -amount }}"
                currency: "{{ currency | default('USD', true) }}"

  - name: Comcast
    match:
      extractor:
        equals: "plaid"
      desc: "Comcast"
    actions:
      - txn:
          payee: "{{ payee }}"
          narration: "Comcast"
          postings:
            - account: "Expenses:Util:Internet:Comcast"
              amount:
                number: "{{ -amount }}"
                currency: "{{ currency | default('USD', true) }}"

With match and variables, you can write:

imports:
  - name: Household expenses
    common_cond:
      extractor:
        equals: "plaid"
    match:
      - cond:
          desc:
            prefix: "PGANDE WEB ONLINE "
        vars:
          account: "Expenses:Util:Gas:PGE"
          narration: "Paid American Express Blue Cash Everyday"
      - cond:
          desc: "Comcast"
        vars:
          account: "Expenses:Housing:Util:Internet:Comcast"
          narration: "Comcast"
    actions:
      - txn:
          payee: "{{ payee }}"
          narration: "{{ narration }}"
          postings:
            - account: "{{ account } "
              amount:
                number: "{{ -amount }}"
                currency: "{{ currency | default('USD', true) }}"

The common_cond is the condition to meet for all the matches. Instead of a map, you define the match with the cond field and the corresponding variables with the vars field. Please note that the vars can also be the Jinja2 template and will rendered before feeding into the transaction template. If there are any original variables from the transaction with the same name defined in the vars field, the variables from the vars field always override.

Omit field in the generated transaction

Sometimes, you may want to omit a particular field in your transactions if the value is unavailable instead of leaving it as a blank string. For example, the payee field sometimes doesn't make sense for some transactions, and the value should not even be present. With a Jinja2 template, it looks like {{ payee }}, but without the payee value provided by the transaction, it will end up with an ugly empty string like this:

2024-02-26 * "" "Interest payment"
  Assets:Bank:US:WellsFargo:Saving                                          0.06 USD
  Income:US:BankInterest                                                   -0.06 USD

To solve the problem, you can use a special variable called omit. The field will be omitted when the rendered value equals the randomly generated omit value. Here's an example:

imports:
  - match:
      desc: "..."
    actions:
      - txn:
          payee: "{{ payee | default(omit, true) }}"
          narration: "{{ narration }}"
          # ...

As a result, if the payee value is not present, the payee field will be absent from the generated transaction like this:

2024-02-26 * "Interest payment"
  Assets:Bank:US:WellsFargo:Saving                                          0.06 USD
  Income:US:BankInterest                                                   -0.06 USD

Import Action Definition

Currently, there are three types of action for matched raw transactions:

• add_txn: Add a transaction to Beancount files
• del_txn: Ensure a transaction is deleted from Beancount files
• ignore: Mark the transaction as processed and ignore it

The type value determines which type of action to use. If the type value is not provided, add_txn will be used by default. Here are the definitions of the available types.

Add Transaction Action

The following keys are available for the add transaction action:

• file: output beancount file name to write the transaction to
• txn: the template of the transaction to insert

A transaction template is an object that contains the following keys:

• id: the optional import-id to overwrite the default one. By default, {{ file | as_posix_path }}:{{ lineno }} will be used unless the extractor provides a default value.
• date: the optional date value to overwrite the default one. By default, {{ date }} will be used.
• flag: the optional flag value to overwrite the default one. By default, * will be used.
• narration: the optional narration value to overwrite the default one. By default {{ desc | default(bank_desc, true) }} will be used.
• payee: the optional payee value of the transaction.
• tags: an optional list of tags for the transaction
• links: an optional list of links for the transaction
• metadata: an optional list of name and value objects as the metadata items for the transaction.
• postings: a list of templates for postings in the transaction.

The structure of the posting template object looks like this.

• account: the account of posting
• amount: the optional amount object with number and currency keys
• price: the optional amount object with number and currency keys
• cost: the optional template of cost spec

Delete Transaction Action

The following keys are available for the delete transaction action:

• txn: the template of the transaction to insert

A deleting transaction template is an object that contains the following keys:

• id: the import-id value for ensuring transactions to be deleted. By default, {{ file | as_posix_path }}:{{ lineno }} will be used unless the extractor provides a default value.

Ignore Action

Sometimes, we are not interested in some transactions, but if we don't process them, you will still see them appear in the "unprocessed transactions" section of the report provided by our command line tool. To mark one transaction as processed, you can simply use the ignore action like this:

- name: Ignore unused entries
  match:
    extractor:
      equals: "mercury"
    desc:
      one_of:
      - Mercury Credit
      - Mercury Checking xx1234
  actions:
    - type: ignore

How it works

Unique import id for transactions extracted from the CSV files

The biggest challenge we face when designing this system is finding a way to deduplicate the imported transactions from CSV. Obviously, we need a way to tell which transactions were already imported into Beancount files so that we don't need to import them again. To make this happen, we introduce the concept of import-id. Each transaction extracted from CSV files should have a unique import ID for us to identify.

In this way, we can process the existing Beancount files and find out which transactions have already been imported. We add a metadata item with the key import-id to the transaction.

Here's an example:

2024-04-15 * "Circleci"
  import-id: "<unique import id>"
  Assets:Bank:US:MyBank                              -30.00 USD
  Expenses:Engineering:ServiceSubscription            30.00 USD

The next question will then be: What should be the unique ID for identifying each transaction in the CSV files? If the CSV files come with an ID column that already has a unique value, we can surely use it. However, what if there's no such value in the file? As we observed, most CSV files exported from the bank come with rows ordered by date.

The straightforward idea is to use filename + lineno as the id. The Jinja2 template would look like this:

{{ file }}:{{ lineno }}

Then with a transaction from row 123 in the file import-data/mybank/2024.csv should have an import ID like this:

import-data/mybank/2024.csv:123

As most of the bank transactions export CSV files have transactions come in sorted order by date, even if there are new transactions added and we export the CSV file for the same bank again and overwrite the existing file, there will only be new lines added at the bottom of the file.

The line number of older transactions from the same CSV file with the same export time range and filter settings should remain the same. The file name and line number serve as a decent default unique identifier for the transactions from CSV files.

Although this approach works for most CSV files sorted by date in ascending order, it won't work for files in descending order. For example, CSV files exported from Mercury came in descending order. Obviously, any new transactions added to the export file will change the line number for all previously imported transactions. To overcome the problem, we also provide reverse_lineno attribute in the extracted transaction. It's the lineno - total_row_count value. As you may have noticed, we intentionally made the number negative. It's trying to make it clear that this line (or row) number is in the reversed order, just like Python's negative index for accessing elements from the end.

With that, we can define the import ID for Mercury CSV files like this:

{{ file }}:{{ reversed_lineno }}

Since each CSV file may have its own unique best way to reliably identify a transaction,each class of extractor can define its own default import ID template.

class YourExtractor(ExtractorBase):

    def get_import_id_template(self) -> str:
        return "{{ file }}:{{ reversed_lineno }}"

The flow of beancount-importer-rules

Now, as you know, we can produce transactions and insert them into Beacount files with unique import IDs so that we can trace them. The next would be putting all the pieces together. Here's the flow diagram of how beanhub-import works:

graph LR
    InputFileList --> CONFIG
    subgraph CONFIG
      direction TB
      EachFile -- file --> ExtractorMatcher
      ExtractorMatcher --> ExtractorFactory
    end

    CONFIG --> EXTRACTION

    subgraph EXTRACTION
      direction TB
      InstantiateFactory -- transactions --> RunExtractor
      RunExtractor -- transactions --> MergeAndGenerate
      MergeAndGenerate -- generated transactions --> MatchAndGenerate
      MatchAndGenerate -- generated transactions --> output
    end

    EXTRACTION --> MERGE
    subgraph MERGE
      transactions --> ComputeChangeset
      ComputeChangeset --> ApplyChangeset
      ApplyChangeset -- apply changes --> OutDir
      OutDir --> CollectExistingTransactions
      CollectExistingTransactions -- beancount transactions --> ComputeChangeset
    end

Step 1. Match input CSV files

Input rules are defined as shown in this example:

inputs:
  - match: "import-data/some-folder/*.csv"
    config:
      extractor: some.valid.python.path:ExtractorClass
      default_file: "books/{{ date.year }}.bean"
      prepend_postings:
        - account: Assets:Bank:US:Mercury
          amount:
            number: "{{ amount }}"
            currency: "{{ currency | default('USD', true) }}"

First, we must find all the matched CSV files based on the rule.

Step 2. Extract transactions from the CSV files

Now that we know which CSV files to extract transactions from, the next step is to use import the extractor, instantiate it, and extract transactions from the CSV files.

      extractor: some.valid.python.path:ExtractorClass

To extract transactions from the CSV files, we need to define an extractor class that inherits from beancount_import_rules.extractors.ExtractorBase or beancount_import_rules.extractors.ExtractorCsvBase.

So if you created extractors/your_extractor.py with the following content:

import decimal
import typing

from beancount_importer_rules.data_types import Transaction
from beancount_importer_rules.extractor import ExtractorCsvBase


class YourCustomCsvExtractor(ExtractorCsvBase):
    name: str = "your-extractor-name"
    fields: typing.List[str] = [
        "Account",
        "Date",
        "SomeFieldWeDontCareAbout",
        "Description",
        "Amount",
        "Balance"
    ]
    date_format: str = "%d/%m/%Y"
    date_field: str = "Date"

    def process_line(self, lineno: int, line: typing.Dict[str, str]) -> Transaction:
        date = self.parse_date(line.pop("Date"))
        description = line.pop("Description")
        amount = decimal.Decimal(line.pop("Amount"))

        return Transaction(
            # The following fields are common to all extractors and required
            extractor=self.name,
            file=self.filename,
            lineno=lineno + 1,
            reversed_lineno=lineno - self.line_count,
            extra=line,

            # The following fields are unique to this extractor
            date=date,
            amount=amount,
            desc=description,
        )

You can then use it in the configuration like this:

inputs:
  - match: "import-data/some-folder/*.csv"
    config:
      extractor: extractors.your_extractor:YourCustomCsvExtractor
      default_file: "books/{{ date.year }}.bean"
      prepend_postings:
        - account: Assets:Bank:US:Mercury
          amount:
            number: "{{ amount }}"
            currency: "{{ currency | default('USD', true) }}"

Step 3. Merge & generate transactions

The design of this step is still working in progress, but we envision you can define "merge" rules like this:

merges:
- match:
  - name: mercury
    extractor:
      equals: "mercury"
    desc: "Credit card payment"
    merge_key: "{{ date }}:{{ amount }}"
  - name: chase
    extractor:
      equals: "chase"
    desc: "Payment late fee"
    merge_key: "{{ post_date }}:{{ amount }}"
  actions:
    - txn:
        narration: "Paid credit card"
        postings:
          - account: Expenses:CreditCardPayment
            amount:
              number: "{{ -mercury.amount }}"
              currency: "{{ mercury.currency | default('USD', true) }}"
          - account: Expenses:LateFee
            amount:
              number: "{{ -chase.amount }}"
              currency: "{{ chase.currency | default('USD', true) }}"

It will match multiple transactions from the CSV input files and generate Beancount transactions accordingly.

Step 4. Match & generate transactions

For CSV transactions not matched in the merge step, we will apply all the matching rules defined in the imports section. Note that the extractor matcher here is referring to the fields attribute on your extractor class.

imports:
- name: Gusto fees
  match:
    extractor:
      equals: "your extractor name"
    desc: GUSTO
  actions:
    - txn:
        narration: "Gusto subscription fee"
        postings:
          - account: Expenses:Office:Supplies:SoftwareAsService
            amount:
              number: "{{ -amount }}"
              currency: "{{ currency | default('USD', true) }}"

If there is a match, corresponding actions, usually adding a transaction, will be performed. The matched CSV transaction attributes will be provided as the values to render the Jinja2 template of the Beancount transaction.

Step 5. Collect existing Beancount transactions

To avoid generating duplicate transactions in the Beancount file, we need to traverse the Beancount folder and find all the existing transactions that were previously imported.

Step 6. Compute change sets

Now, with the generated transactions from the import rules and the existing Beancount transactions we previously inserted into Beancount files, we can compare and compute the required changes to make it up-to-date.

Step 7. Apply changes

Finally, with the change sets generated from the previous step, we use our beancount-parser to parse the existing Beancount files as syntax trees, transform them accordingly, and then write them back with our beancount-black formatter.

And that's it! Now, all the imported transactions are up-to-date.