holy-sheet

Zero-dependency .xlsx writer + reader + formula linter for agentic document creation. The Python mirror of PHP particle-academy/holy-sheet and Node @particle-academy/holy-sheet — same schema in, the same .xlsx out, whichever runtime you happen to be on.

import holy_sheet

schema = {
    "sheets": [
        {
            "name": "Sales",
            "columns": [
                {"header": "Region", "type": "string"},
                {"header": "Revenue", "type": "currency", "currency": "USD"},
            ],
            "rows": [
                ["North", 12000],
                ["South", 9800],
            ],
            "totals": {"Revenue": "sum"},
        }
    ]
}

holy_sheet.write(schema, "sales.xlsx")      # -> {"path": …, "bytes": …, "sheets": 1}
data = holy_sheet.to_bytes(schema)          # bytes, for an HTTP response

The schema is the point

That dict is the whole API. It is declarative and emittable in one shot — an agent describes the workbook it wants and hands it over, rather than driving a builder through forty calls and hoping the state machine agrees. There is no Workbook() to construct, no add_row(), no cursor.

Which is why the input is a plain dict, not a dataclass. The validator is the gate, not the type system:

holy_sheet.validate(schema)            # [] means valid; otherwise structured errors
holy_sheet.validate_and_repair(schema) # fixes the unambiguous mistakes, reports what it fixed
holy_sheet.lint(schema)                # evaluates every formula, reports the broken ones

validate_and_repair exists precisely because models send slightly-wrong JSON: a singular sheet key, row where rows belongs, an integer-keyed rows object, "1200" where a number goes. A dataclass would move the gate into a constructor and reject exactly the input the repairer is there to rescue. holy_sheet.schema.types carries TypedDicts for editor autocomplete; they are documentation, not constructors.

lint catches what an LLM actually gets wrong with formulas — referencing the header row instead of the first data row, a string in arithmetic, a cell that does not exist, a circular dependency — and says what to do about it:

>>> holy_sheet.lint({"sheets": [{"name": "Q4", "rows": [
...     ["Region", "Annual", "Monthly"],
...     ["NA", 12000, {"formula": "B1*12"}],
... ]}]})
[{'sheet': 'Q4', 'address': 'C2', 'formula': 'B1*12', 'error': '#VALUE!',
  'hint': 'Arithmetic on a non-numeric cell: B1 = "Annual" (string) '
          'Did you mean B2? (it holds 12000)'}]

The Agent API

Module-level functions — no class to instantiate, no DI container:

tool_definition() is byte-identical across all three engines and checksum-pinned in each — drop it into an Anthropic tool_use block or an OpenAI function definition and every backend describes the same tool.

Lower-level services are exported under their peer names for when you want to inject them: Validator, Repairer, Normalizer, FormulaLinter, Inference, Theme, XlsxWriter, XlsxReader, OdsReader, FormatSniffer, ArrayBuilder, CsvBuilder, CellAddress, SheetDiff, SheetReducer, SheetOpSchema, SchemaException, UnsupportedFormatException.

Reading OpenDocument spreadsheets

read() and describe() accept an OpenDocument spreadsheet (.ods) as well as an .xlsx, and return the same schema for both, so a caller needs no branch on the file type and no second library:

schema = holy_sheet.describe("upload.ods")  # or upload.xlsx: same shape

The format is decided from the file's contents, never its name. Anything else raises UnsupportedFormatException (a RuntimeError, with the declared mimetype when there is one). What maps and what does not is listed in the PHP package's docs/ReadPath.md; this port reads the same fixtures and is diffed against it.

Versions as ops

An agent that edits a workbook needs a history, and hashing xlsx bytes cannot keep a one-cell edit small: a zip changes nearly every byte. diff keeps each version as the ops that restore it instead.

ops = holy_sheet.diff(new, old)          # store these with the new version
old_again = holy_sheet.reduce(new, ops)  # equals `old`, key order aside

• reduce(a, diff(a, b)) equals b. The ops are verified by replaying them; a sheet they cannot reproduce is replaced whole, and as a last resort so is the workbook.
• Small edits stay small. One changed cell is one set_cell. Rows and columns are aligned by content first, so an inserted row is one insert_rows plus its cells.
• A save without a change records nothing. Schemas that write the same workbook diff to []: an authored columns/rows sheet and the cells describe() reads back from it, or a schema without meta.created and its written copy. equivalent(a, b) is that check on its own. Both schemas must be valid, because the check writes them.
• reduce is pure. Nothing passed in is modified, the result shares no mutable structure with it, and an op naming a sheet that is not there is skipped rather than raised.

The ops: set_cell, set_range, set_workbook (fancy-sheets' SheetOp shapes, with its semantics: a set_cell without formula clears the formula and keeps the format and comment, null clears those), clear_cell, insert_rows, delete_rows, insert_columns, delete_columns, add_sheet, remove_sheet, rename_sheet, move_sheet, replace_sheet, set_merged_regions, set_column_widths, set_frozen and set_meta. op_schema() is the JSON Schema for one of them, to validate stored ops or to hand an LLM as a tool.

Row and column ops move cells, merged regions and column widths; they do not rewrite formula text. After a column insert or delete, columnWidths has integer keys, the keys describe() returns, even where the schema came from JSON with string keys.

The same input gives the same ops, in the same order, as PHP's Agent::diff, so a history written by a Laravel app replays here and the other way round. The parity suite runs the PHP package and compares op lists.

Moving between runtimes

The schema does not change. Only the call shape does.

Three differences worth knowing, each deliberate:

• write is synchronous. PHP's is; Node's is async only because browsers have no synchronous filesystem, which is not a constraint Python shares.
• from_csv accepts a path as well as content, following PHP. Node takes content only, because it targets browsers.
• read takes bytes and describe takes a path, which is Node's split rather than PHP's path-only reader. Bytes are the better primitive: an upload, a response body and a file all work.

What it writes

Multiple sheets · inline-string text cells · deduplicated fonts/fills/borders/numFmts in styles.xml · merged regions · column widths · frozen panes · comments (comments1.xml + vmlDrawing1.vml) · formulas with optional cached values · symbolic totals ({"Revenue": "sum"} becomes SUM(B2:B4)) · four themes.

Exactly those parts and no others — no sharedStrings.xml, no calcChain.xml, no theme1.xml. Those are the classic sources of xlsx diff noise and every engine in this family deliberately skips them. Output is deterministic: the same input produces the same bytes, always.

No dependencies, permanently

zipfile and xml.etree are standard library and are generic infrastructure. There is deliberately no openpyxl, no xlsxwriter, no lxml.

This is not minimalism for its own sake. The schema model is the product, and an all-in-one spreadsheet library would own it — along with the XML layout, which is the cross-runtime contract. The three engines agree at the level of part bytes: attribute order, self-closing style, the absence of inter-element whitespace, ' rather than '. A library owns every one of those decisions and cannot be talked out of them, so tests/test_parity_php.py — which runs the PHP engine as a subprocess and diffs each OOXML part — would fail on the first fixture.

Reading is different: xml.etree does that work, because nothing is serialised there.

Install

pip install fancy-holy-sheet

Requires Python 3.11+.

Development

python -m pytest

The suite includes cross-runtime parity against the PHP engine. It needs php on PATH (or PHP_BIN pointing at an interpreter) and a checkout of the PHP package beside this one (or HOLY_SHEET_PHP_SRC). Locally a missing toolchain skips those tests, loudly. Under CI it fails — a parity suite that silently stops comparing anything reads exactly like one that compares everything, and that is how two sibling suites reported green over zero cross-engine coverage for months.

The rest of the family

holy-sheet writes spreadsheets. Its siblings write the other two formats an agent gets asked for, with the same declarative-schema shape:

• dark-slide — .pptx
• last-word — .docx

Part of the Fancy UI suite.

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