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openpyxl vs python-calamine: which one reads more real-world Excel (.xlsx) files?
openpyxl 3.1.5 and python-calamine 0.9.1 on the same 353 odd real-world files from Apache POI test files (bug reports, fuzzers, broken exporters). Measured, not opinion; re-tested by itself on every new PyPI release. Updated 06 November 2026.
More files readpython-calamine293 vs 286
Faster on this setpython-calamine2.0 s vs 19.4 s total (10× faster)
Both read282only openpyxl: 4 · only python-calamine: 11
python-calamine got text from more files: 293 vs 286 of 353. openpyxl broke (error, hang or crash) on 5 files that python-calamine read; python-calamine broke on 2 files that openpyxl read.
| Library | Text from | 🔴 Fails where the other reads | 🟡 Empty where the other reads | ⏱ Hangs or crashes | Median ms/file | Total seconds |
|---|---|---|---|---|---|---|
| openpyxl 3.1.5 | 286 | 5 | 6 | 0 | 6 | 19.4 |
| python-calamine 0.9.1 | 293 | 2 | 2 | 0 | <1 | 2.0 |
Files only openpyxl reads (4)
| 49783.xlsx | python-calamine: no text |
| duplicate-filename-case-insensitive.xlsx | python-calamine: no text |
| poc-shared-strings.xlsx | python-calamine: CalamineError: Range is missing the expected row component. |
| xlsx-corrupted.xlsx | python-calamine: XmlError: Relationships |
Files only python-calamine reads (11)
| 123233_charts.xlsx | openpyxl: no text |
| 49609.xlsx | openpyxl: KeyError: "There is no item named '[Content_Types].xml' in the archive" |
| 52348.xlsx | openpyxl: no text |
| 57914.xlsx | openpyxl: no text |
| LIBRE_OFFICE-128382-0.xlsx | openpyxl: TypeError: expected <class 'openpyxl.styles.fills.Fill'> |
| SampleSS.strict.xlsx | openpyxl: no text |
| SimpleStrict.xlsx | openpyxl: no text |
| clusterfuzz-testcase-minimized-POIXSSFFuzzer-5937385319563264.xlsx | openpyxl: BadZipFile: Bad CRC-32 for file 'xl/worksheets/sheet8.xml' |
| picture.xlsx | openpyxl: TypeError: CellStyle.__init__() got an unexpected keyword argument 'ZMIENNA_contentFontsCount' |
| sample.strict.xlsx | openpyxl: no text |
| style-alternate-content.xlsx | openpyxl: TypeError: <class 'openpyxl.styles.named_styles._NamedCellStyle'>.name should be <class 'str'> but value is <class 'NoneType'> |
What this does not tell you
This compares not breaking: whether each library gets any text out of each file. It does not rank text quality (reading order, tables, headings), and speed is one GitHub-hosted runner, default settings, no OCR switched on. If you need structure for RAG, also look at the output on your own files.
How this is measured
- Each library runs a short recipe from its own docs (board/targets.py):
open the file, get all text. Installed with the extras the docs recommend for reading
(
pypdf[full]: AES decryption, Brotli), nothing else. One worker process per CPU; per file 60 s / 120 s / 180 s / 300 s / 600 s at most (the any-document table allows longer: some tools load models), killed above the memory limit. - Fails where another reads: the library raised an error, hung or crashed on a file from which another library in the same table got text. Files that every library fails on (encrypted, truncated, fuzzed) are not counted against anyone.
- Empty where another reads: no error, but no text. This is often the recipe, not the library: for example
python-docx's paragraphs+tables recipe skips headers, text boxes and nested tables. Check the file list. - Any document → text: a file type the tool's docs don't list, or that the tool itself rejects as unsupported, counts as "not supported", not as a failure (lists in board/libs.json). Returning a file's raw RTF source counts as empty, for every tool. Each tool runs with default settings: no OCR switched on by hand.
- OCR: each image comes with the human-written ground-truth text published with its dataset. Words found is the share of its words that appear anywhere in the engine's output (reading order doesn't matter); an image that fails or comes back empty counts as 0. The ground truth of receipts and document pages covers only their annotated text, so a character error rate would punish engines for reading more than was annotated; it is in the raw results but not ranked. English models, CPU, default settings.
- Speech: each clip comes with its dataset's reference transcript. Both texts go through Whisper's English text normalizer (case, punctuation, "twenty" = "20"); word error rate is all substituted, missing and extra words over all reference words, the usual corpus-level WER. A clip that fails or comes back empty counts all its words as errors. The three Whisper implementations use the same base.en model; each other engine its documented default model. English, CPU, default decoding settings.
- Language detection: each text's language is known from Tatoeba. An answer counts as correct if the library's code matches after mapping variants to ISO 639-1 (zh-cn → zh, nb → no, iw → he). Close languages count as different: Croatian detected as Bosnian or Serbian, or Norwegian as Danish, is wrong. One call per text with default settings and all languages enabled.
- PDF → Markdown: pages from AI2's olmOCR-bench (ODC-BY), scored with its own checks (vendored, Apache-2.0): a sentence must be present, a page header or footer absent, two passages in the right order, a table cell next to the right neighbour. Checks passed is all passed checks over all checks; a page that fails or comes back empty passes none. Math pages are left out (their checks need a browser to render formulas). Default settings: whatever OCR a tool does on its own, it does.
- Text quality (order, tables, layout) is not ranked in the other tables; they are about not breaking. The raw results have every output's size and hash.
- Same files for every version: the test collections are pinned to one commit. GitHub-hosted runner, so times are comparable within one table, roughly.