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mimetypes.add_type should complain when you give it an undotted ext #75223

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mimetypes.add_type should complain when you give it an undotted ext#75223

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3.7 (EOL)end of lifeend of lifedocsDocumentation in the Doc dirDocumentation in the Doc dirstdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

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OddBloke

mannequin

opened

on Jul 25, 2017

Issue body actions

BPO	31040
Nosy	@OddBloke, @JimJJewett, @JulienPalard, @rcj4747
PRs	bpo-31040: Add warning note about mimetypes.add_type ext argument format #2871 gh-75223: Reject undotted extensions in `mimetypes.add_type()` #2895

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-07-25.19:25:41.891>
labels = ['3.7', 'library', 'docs']
title = 'mimetypes.add_type should complain when you give it an undotted ext'
updated_at = <Date 2019-09-13.10:59:42.020>
user = 'https://github.com/OddBloke'

bugs.python.org fields:

activity = <Date 2019-09-13.10:59:42.020>
actor = 'mdk'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation', 'Library (Lib)']
creation = <Date 2017-07-25.19:25:41.891>
creator = 'odd_bloke'
dependencies = []
files = []
hgrepos = []
issue_num = 31040
keywords = []
message_count = 4.0
messages = ['299135', '306501', '352266', '352286']
nosy_count = 5.0
nosy_names = ['odd_bloke', 'docs@python', 'Jim.Jewett', 'mdk', 'rcj']
pr_nums = ['2871', '2895']
priority = 'normal'
resolution = None
stage = 'commit review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue31040'
versions = ['Python 3.7']

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OddBloke commented on Jul 25, 2017
OddBlokemannequin
on Jul 25, 2017
MannequinAuthor
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import mimetypes print(mimetypes.guess_type('foo.manifest')) mimetypes.add_type('text/plain', 'manifest') print(mimetypes.guess_type('foo.manifest'))

results in:

('application/x-ms-manifest', None) ('application/x-ms-manifest', None)

I (mistakenly) expected the latter print to give me "('text/plain', None)". It doesn't because I should have prepended a . to the second add_type argument.

I think add_type should error out when given an extension without a dot-prefix, because it's extremely unlikely that code that does so is behaving as intended with the current implementation.

(At the very least, documentation should be updated to make this expectation clearer.)
OddBloke
added
stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory
on Jul 25, 2017
Mariatta
added
docsDocumentation in the Doc dirDocumentation in the Doc dir

3.7 (EOL)end of lifeend of life
on Jul 26, 2017
Mariatta
assigned
docspython
on Jul 26, 2017
jimjjewett commented on Nov 19, 2017
jimjjewettmannequin
on Nov 19, 2017
Mannequin
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Ideally, use .startswith('.') Instead if find, but this is a clear UI fix. First pull request fixes doc, second fixes code. OK to apply both.
JulienPalard commented on Sep 13, 2019
JulienPalard
on Sep 13, 2019
Member
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I think we should deprecate calling add_type with an empty ext, as I don't think it's a feature, more a side effect of the current implementation.

But as some may use it like a feature, I asked the current PR to emit a warning, to not break the current implementations.

To be able to simplify in the future, why not deprecating empty ext so we can remove it in a few versions?
JulienPalard commented on Sep 13, 2019
JulienPalard
on Sep 13, 2019
Member
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I just found a case where the empty mime type is actually usefull, it's in Lib/http/server.py:

extensions_map = mimetypes.types_map.copy() extensions_map.update({ '': 'application/octet-stream', # Default '.py': 'text/plain', '.c': 'text/plain', '.h': 'text/plain', })

It does *not* uses add_type, but demos the fact that the empty type may be usefull from time to time, maybe don't warn and don't deprecate it at all.
ezio-melotti
transferred this issue from on Apr 10, 2022

hugovk commented on Nov 21, 2024

hugovk

on Nov 21, 2024

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Checking the top 8k PyPI projects:

Details

❯ python3 ~/github/misc/cpython/search_pypi_top.py -q . mimetypes.add_type
./django_pipeline-3.1.0.tar.gz: django_pipeline-3.1.0/pipeline/utils.py: mimetypes.add_type(type, ext)
./dagster-webserver-1.9.0.tar.gz: dagster-webserver-1.9.0/dagster_webserver/webserver.py: mimetypes.add_type("application/javascript", ".js")
./dagster-webserver-1.9.0.tar.gz: dagster-webserver-1.9.0/dagster_webserver/webserver.py: mimetypes.add_type("text/css", ".css")
./dagster-webserver-1.9.0.tar.gz: dagster-webserver-1.9.0/dagster_webserver/webserver.py: mimetypes.add_type("image/svg+xml", ".svg")
./dash-2.18.1.tar.gz: dash-2.18.1/dash/dash.py: mimetypes.add_type("application/json", ".map", True)
./chainlit-1.3.1.tar.gz: chainlit-1.3.1/chainlit/server.py: mimetypes.add_type("application/javascript", ".js")
./chainlit-1.3.1.tar.gz: chainlit-1.3.1/chainlit/server.py: mimetypes.add_type("text/css", ".css")
./ansible-10.5.0.tar.gz: ansible-10.5.0/ansible_collections/azure/azcollection/plugins/modules/azure_rm_storageblob.py: mimetypes.add_type('application/json', '.json')
./ansible-10.5.0.tar.gz: ansible-10.5.0/ansible_collections/azure/azcollection/plugins/modules/azure_rm_storageblob.py: mimetypes.add_type('application/javascript', '.js')
./ansible-10.5.0.tar.gz: ansible-10.5.0/ansible_collections/azure/azcollection/plugins/modules/azure_rm_storageblob.py: mimetypes.add_type('application/wasm', '.wasm')
./django_filer-3.2.3.tar.gz: django_filer-3.2.3/filer/apps.py: mimetypes.add_type("image/heic", ext)
./django_filer-3.2.3.tar.gz: django_filer-3.2.3/filer/apps.py: mimetypes.add_type("image/webp", ".webp")
./EbookLib-0.18.tar.gz: EbookLib-0.18/ebooklib/utils.py: mimetypes.add_type('application/xhtml+xml', '.xhtml')
./fava-1.29.tar.gz: fava-1.29/src/fava/application.py: mimetypes.add_type("text/javascript", ".js")
./ansible-10.5.0.tar.gz: ansible-10.5.0/ansible_collections/community/general/tests/integration/targets/launchd/files/ansible_test_service.py: mimetypes.add_type('application/json', '.json')
./azure_cli-2.65.0.tar.gz: azure_cli-2.65.0/azure/cli/command_modules/storage/util.py: mimetypes.add_type('application/json', '.json')
./azure_cli-2.65.0.tar.gz: azure_cli-2.65.0/azure/cli/command_modules/storage/util.py: mimetypes.add_type('application/javascript', '.js')
./azure_cli-2.65.0.tar.gz: azure_cli-2.65.0/azure/cli/command_modules/storage/util.py: mimetypes.add_type('application/wasm', '.wasm')
./jupyter_server-2.14.2.tar.gz: jupyter_server-2.14.2/jupyter_server/serverapp.py: mimetypes.add_type("text/css", ".css")
./jupyter_server-2.14.2.tar.gz: jupyter_server-2.14.2/jupyter_server/serverapp.py: mimetypes.add_type("application/javascript", ".js")
./jupyter_server-2.14.2.tar.gz: jupyter_server-2.14.2/jupyter_server/serverapp.py: mimetypes.add_type("application/wasm", ".wasm")
./jupyterlab_server-2.27.3.tar.gz: jupyterlab_server-2.27.3/jupyterlab_server/licenses_handler.py: mimetypes.add_type("text/markdown", ".md")
./locust-2.32.1.tar.gz: locust-2.32.1/locust/web.py: mimetypes.add_type("application/javascript", ".js")
./openpyxl-3.1.5.tar.gz: openpyxl-3.1.5/openpyxl/packaging/manifest.py: mimetypes.add_type('application/xml', ".xml")
./openpyxl-3.1.5.tar.gz: openpyxl-3.1.5/openpyxl/packaging/manifest.py: mimetypes.add_type('application/vnd.openxmlformats-package.relationships+xml', ".rels")
./openpyxl-3.1.5.tar.gz: openpyxl-3.1.5/openpyxl/packaging/manifest.py: mimetypes.add_type("application/vnd.ms-office.vbaProject", ".bin")
./openpyxl-3.1.5.tar.gz: openpyxl-3.1.5/openpyxl/packaging/manifest.py: mimetypes.add_type("application/vnd.openxmlformats-officedocument.vmlDrawing", ".vml")
./openpyxl-3.1.5.tar.gz: openpyxl-3.1.5/openpyxl/packaging/manifest.py: mimetypes.add_type("image/x-emf", ".emf")
./panel-1.5.3.tar.gz: panel-1.5.3/panel/io/resources.py: mimetypes.add_type("application/javascript", ".js")
./platformio-6.1.16.tar.gz: platformio-6.1.16/platformio/home/cli.py: mimetypes.add_type("text/html", ".html")
./platformio-6.1.16.tar.gz: platformio-6.1.16/platformio/home/cli.py: mimetypes.add_type("text/css", ".css")
./platformio-6.1.16.tar.gz: platformio-6.1.16/platformio/home/cli.py: mimetypes.add_type("application/javascript", ".js")
./nicegui-2.5.0.tar.gz: nicegui-2.5.0/nicegui/nicegui.py: mimetypes.add_type('text/javascript', '.js')
./nicegui-2.5.0.tar.gz: nicegui-2.5.0/nicegui/nicegui.py: mimetypes.add_type('text/css', '.css')
./robocorp_storage-1.0.5.tar.gz: robocorp_storage-1.0.5/src/robocorp/storage/__init__.py: mimetypes.add_type(type_, ext)
./prefect-3.1.0.tar.gz: prefect-3.1.0/src/prefect/server/api/server.py: mimetypes.add_type("application/javascript", ".js")
./streamlit-1.39.0.tar.gz: streamlit-1.39.0/streamlit/web/server/app_static_file_handler.py: mimetypes.add_type("image/webp", ".webp")
./streamlit-1.39.0.tar.gz: streamlit-1.39.0/streamlit/web/server/component_request_handler.py: mimetypes.add_type("text/html", ".html")
./streamlit-1.39.0.tar.gz: streamlit-1.39.0/streamlit/web/server/component_request_handler.py: mimetypes.add_type("application/javascript", ".js")
./streamlit-1.39.0.tar.gz: streamlit-1.39.0/streamlit/web/server/component_request_handler.py: mimetypes.add_type("text/css", ".css")
./supervisely-6.73.221.tar.gz: supervisely-6.73.221/supervisely/convert/image/image_converter.py: mimetypes.add_type("image/heic", ".heic")  # to extend types_map
./supervisely-6.73.221.tar.gz: supervisely-6.73.221/supervisely/convert/image/image_converter.py: mimetypes.add_type("image/heif", ".heif")  # to extend types_map
./supervisely-6.73.221.tar.gz: supervisely-6.73.221/supervisely/convert/image/image_converter.py: mimetypes.add_type("image/jpeg", ".jfif")  # to extend types_map
./supervisely-6.73.221.tar.gz: supervisely-6.73.221/supervisely/convert/image/image_converter.py: mimetypes.add_type("image/avif", ".avif")  # to extend types_map
./supervisely-6.73.221.tar.gz: supervisely-6.73.221/supervisely/convert/image/image_converter.py: mimetypes.add_type("image/bmp", ".bmp")  # to extend types_map
./supervisely-6.73.221.tar.gz: supervisely-6.73.221/supervisely/convert/image/image_helper.py: mimetypes.add_type("image/webp", ".webp")  # to extend types_map
./supervisely-6.73.221.tar.gz: supervisely-6.73.221/supervisely/convert/image/image_helper.py: mimetypes.add_type("image/jpeg", ".jfif")  # to extend types_map
./python_semantic_release-9.12.0.tar.gz: python_semantic_release-9.12.0/semantic_release/hvcs/github.py: mimetypes.add_type("application/octet-stream", ".whl")
./python_semantic_release-9.12.0.tar.gz: python_semantic_release-9.12.0/semantic_release/hvcs/github.py: mimetypes.add_type("text/markdown", ".md")
./sqlmesh-0.130.1.tar.gz: sqlmesh-0.130.1/web/server/main.py: mimetypes.add_type("application/javascript", ".js")
./sqlmesh-0.130.1.tar.gz: sqlmesh-0.130.1/web/server/main.py: mimetypes.add_type("text/css", ".css")
./trame-3.7.0.tar.gz: trame-3.7.0/trame/app/mimetypes.py: mimetypes.add_type(key, value)
./trame-3.7.0.tar.gz: trame-3.7.0/trame/app/mimetypes.py: mimetypes.add_type(type, ext)
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('image/png', '.png')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('image/jpeg', '.jpeg')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('image/webp', '.webp')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('image/gif', '.gif')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('image/bmp', '.bmp')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('image/x-tga', '.tga')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('image/tiff', '.tiff')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('image/vnd.adobe.photoshop', '.psd')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('video/mp4', '.mp4')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('video/quicktime', '.mov')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('video/avi', '.avi')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('audio/mpeg', '.mp3')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('audio/m4a', '.m4a')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('audio/aac', '.aac')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('audio/ogg', '.ogg')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('audio/flac', '.flac')
./Telethon-1.37.0.tar.gz: Telethon-1.37.0/telethon/utils.py: mimetypes.add_type('application/x-tgsticker', '.tgs')
./webob-1.8.9.tar.gz: webob-1.8.9/src/webob/static.py: mimetypes.add_type('text/javascript', '.js') # stdlib default is application/x-javascript
./webob-1.8.9.tar.gz: webob-1.8.9/src/webob/static.py: mimetypes.add_type('image/x-icon', '.ico') # not among defaults
./webob-1.8.9.tar.gz: webob-1.8.9/tests/test_request.py: mimetypes.add_type('application/x-foo', '.foo')
./pyvo-1.6.tar.gz: pyvo-1.6/pyvo/dal/mimetype.py: mimetypes.add_type('application/fits', 'fits')
./pyvo-1.6.tar.gz: pyvo-1.6/pyvo/dal/mimetype.py: mimetypes.add_type('application/x-fits', 'fits')
./pyvo-1.6.tar.gz: pyvo-1.6/pyvo/dal/mimetype.py: mimetypes.add_type('image/fits', 'fits')
./pyvo-1.6.tar.gz: pyvo-1.6/pyvo/dal/mimetype.py: mimetypes.add_type('text/plain', 'txt')

Time: 0:00:26.975038
Found 77 matching lines in 26 projects

Of the 77 calls (in 26 projects) to mimetypes.add_type:

68 are dotted
5 (in 4 projects) use a variable. I checked them and the variable uses dotted input.
4 (in 1 project) are undotted. I opened a PR: Add dot to extensions of added MIME types astropy/pyvo#622

hugovk
added a commit that references this issue on Apr 28, 2025
gh-75223: Deprecate undotted extensions in `mimetypes.MimeTypes.add_t…
ee9102a
hugovk commented on Apr 28, 2025
hugovk
on Apr 28, 2025
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Deprecate in 3.14: gh-75223: Deprecate undotted extensions in mimetypes.MimeTypes.add_type #128638

Remove in 3.16
StanFromIreland
closed this as a duplicateof Remove deprecated feature: ext must start with . in mimetypes.add_type #149720 on May 12, 2026

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mimetypes.add_type should complain when you give it an undotted ext #75223

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OddBloke commented on Jul 25, 2017

jimjjewett commented on Nov 19, 2017

JulienPalard commented on Sep 13, 2019

JulienPalard commented on Sep 13, 2019

hugovk commented on Nov 21, 2024

hugovk commented on Apr 28, 2025

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