Feature request: show balance sheets over date range

[dharmatech]

Introduction

I'm using ledger-cli to model what happens to treasury, federal reserve, and bank balance sheets given certain economic actions.

Here's a small 4 transaction example:

2020-01-01 bank borrows 1000 from fed
    bank:assets:reserves:fed          1000
    bank:liabilities:loan:fed        -1000
    ;
    fed:assets:loans:bank             1000
    fed:liabilities:deposits:odhbdi  -1000


2020-02-01 bank buys bonds from treasury
    bank:assets:bonds                   1000
    bank:assets:reserves               -1000
    ;
    treasury:liabilities:treasury_debt  -1000
    treasury:assets:reserves             1000
    ;
    fed:liabilities:deposits:odhbdi     1000    ; other deposits held by depository institutions
    fed:liabilities:deposits:tga       -1000    ; treasury general account


2020-03-01 treasury pays person for road using bank
    treasury:assets:reserves                  -1000
    treasury:expenses:road                     1000
    ;
    bank:assets:reserves:fed                  1000
    bank:liabilities:deposits:person         -1000
    ;
    person:equity:earnings:road               -1000
    person:assets:deposits:bank                1000


2020-04-01 bank repays fed loan
    bank:liabilities:loan:fed                 1000
    bank:assets:reserves:fed                 -1000
    ;
    fed:assets:loans:bank                    -1000
    fed:liabilities:deposits:odhbdi           1000

Displaying the balance sheets over time

I then display the balance sheet after each transaction, with a description of what led to that state.

This requires that I run something like the following (in PowerShell):

Write-Output 'bank borrows 1000 from fed'
ledger -f tmp.ledger balance --end 2020-01-02
       
Write-Output 'bank buys bonds from treasury'
ledger -f tmp.ledger balance --end 2020-02-02
       
Write-Output 'treasury pays person for road using bank'
ledger -f tmp.ledger balance --end 2020-03-02

The output looks like this:

Feature request

Instead of doing the above, it would be nice to be able to specify that I want to see the balance sheets at various points in time:

ledger -f tmp.ledger balance-sheets 2020-01-02, 2020-02-02, 2020-03-02

Then ledger could take care of showing a description taken from the transaction as well as the resulting balance sheet.

Maybe also support date ranges:

ledger -f tmp.ledger balance-sheets --start 2020-01-02 --end 2020-03-02

And if no dates are specified, the state after each transaction is shown:

ledger -f tmp.ledger balance-sheets

Potential other uses

Even if folks aren't using ledger-cli in the above (admittedly probably unusual) way, it might be helpful for when folks are debugging transactions.

[dharmatech]

Here's my workaround using the ledger Python API.

api-balance.py:

import ledger
from core import *
from history_of_balances import *

ls = [xact for xact in ledger.read_journal('tmp.ledger').xacts()]

ledger_ = Ledger()

for transaction in ls:
    ledger_.transactions.append(
        Transaction(
            transaction.date, 
            transaction.payee,
            [Entry(str(post.account), float(post.amount)) for post in transaction.posts()]))

history_of_balances(ledger_)

If I run:

python3 -m api-balance

I get the following (screenshot truncated due to length):

The core and history_of_balances modules are from this library:

https://github.com/dharmatech/minimal_ledger.py