Nbconvert

Execute preprocessor no longer add illegal execution counts to markdown
cells [1396](https://github.com/jupyter/nbconvert/pull/1396)

A patch for a few minor issues raised out of the 6.0 release.

Comprehensive notes

Fixing Problems

- Added windows work-around fix in CLI for async applications
[1383](https://github.com/jupyter/nbconvert/pull/1383)
- Fixed pathed template files to behave correctly for local relative
paths without a dot [1381](https://github.com/jupyter/nbconvert/pull/1381)
- ExecuteProcessor now properly has a `preprocess_cell` function to
overwrite [1380](https://github.com/jupyter/nbconvert/pull/1380)

Testing, Docs, and Builds

- Updated README and docs with guidance on how to get help with
nbconvert [1377](https://github.com/jupyter/nbconvert/pull/1377)
- Fixed documentation that was referencing `template_path` instead of
`template_paths` [1374](https://github.com/jupyter/nbconvert/pull/1374)

A quick patch to fix an issue with get_exporter [1367](https://github.com/jupyter/nbconvert/pull/1367)

significant changes.

- Python 2 support was dropped. Currently Python 3.6-3.8 is supported
and tested by nbconvert. However, nbconvert 6.0 provides limited
support for Python 3.6. nbconvert 6.1 will drop support for Python
3.6. Limited support means we will test and run CI on Python 3.6.12
or higher. Issues that are found only affecting Python 3.6 are not
guaranteed to be fixed. We recommend all users of nbconvert use
Python 3.7 and higher.
- Unlike previous versions, nbconvert 6.0 relies on the
[nbclient](https://github.com/jupyter/nbclient/) package for the
execute preprocessor, which allows for asynchronous kernel requests.
- `template_path` has become `template_paths`. If referring to a 5.x
style `.tpl` template use the full path with the `template_file`
argument to the file. On the command line the pattern is
`--template-file=<path/to/file.tpl>`.
- Nbconvert 6.0 includes a new "webpdf" exporter, which renders
notebooks in pdf format through a headless web browser, so that
complex outputs such as HTML tables, or even widgets are rendered in
the same way as with the HTML exporter and a web browser.
- The default template applied when exporting to HTML now produces the
same DOM structure as JupyterLab, and is styled using JupyterLab's
CSS. The pygments theme in use mimics JupyterLab's codemirror mode
with the same CSS variables, so that custom JupyterLab themes could
be applied. The classic notebook styling can still be enabled with

bash
jupyter nbconvert --to html --template classic


- Nbconvert 6.0 includes a new system for creating custom templates,
which can now be installed as packages. A custom "foobar" template
is installed in Jupyter's data directory under
`nbconvert/templates` and has the form of a directory containing all
resources. Templates specify their base template as well as other
configuration parameters in a `conf.json` at the root of the
template directory.
- The "slideshow" template now makes use of RevealJS version 4. It
can now be used with the HTML exporter with

bash
jupyter nbconvert --to html --template reveal


The `--to slides` exporter is still supported for convenience.

- Inkscape 1.0 is now supported, which had some breaking changes that
prevented 5.x versions of nbconvert from converting documents on
some systems that updated.

Remaining changes

We merged 105 pull requests! Rather than enumerate all of them we'll
link to the github page which contains the many smaller impact
improvements.

The full list can be seen [on
GitHub](https://github.com/jupyter/nbconvert/issues?q=milestone%3A6.0+)

The following authors and reviewers contributed the changes for this
release -- Thanks you all!

- Charles Frye
- Chris Holdgraf
- Felipe Rodrigues
- Gregor Sturm
- Jim
- Kerwin Sun
- Ryan Beesley
- Matthew Seal
- Matthias Geier
- thuy-van
- Tyler Makaro

Significant Changes

RegExRemove applies to all cells

RegExRemove preprocessor now removes cells regardless of cell outputs.
Before this only cells that had outputs were filtered.

Comprehensive notes

New Features

- Add support for alt tags for jpeg and png images
[1112](https://github.com/jupyter/nbconvert/pull/1112)
- Allow HTML header anchor text to be HTML [1101](https://github.com/jupyter/nbconvert/pull/1101)
- Change RegExRemove to remove code cells with output
[1095](https://github.com/jupyter/nbconvert/pull/1095)
- Added cell tag data attributes to HTML exporter
[1090](https://github.com/jupyter/nbconvert/pull/1090) and
[1089](https://github.com/jupyter/nbconvert/pull/1089)

Fixing Problems

- Update svg2pdf.py to search the PATH for inkscape
[1115](https://github.com/jupyter/nbconvert/pull/1115)
- Fix latex dependencies installation command for Ubuntu systems
[1109](https://github.com/jupyter/nbconvert/pull/1109)

Testing, Docs, and Builds

- Added Circle CI builds for documentation [1114](https://github.com/jupyter/nbconvert/pull/1114) [#1120](https://github.com/jupyter/nbconvert/pull/1120), and
[1116](https://github.com/jupyter/nbconvert/pull/1116)
- Fix typo in argument name in docstring (TagRemovePreprocessor)
[1103](https://github.com/jupyter/nbconvert/pull/1103)
- Changelog typo fix [1100](https://github.com/jupyter/nbconvert/pull/1100)
- Updated API page for TagRemovePreprocessor and TemplateExporter
[1088](https://github.com/jupyter/nbconvert/pull/1088)
- Added remove_input_tag traitlet to the docstring
[1088](https://github.com/jupyter/nbconvert/pull/1088)

The following 24 authors and reviewers contributed 224 commits -- Thank
you all!

- 00Kai0
- Aidan Feldman
- Alex Rudy
- Alexander Kapshuna
- Alexander Rudy
- amniskin
- Carol Willing
- Dustin H
- Hsiaoming Yang
- imtsuki
- Jessica B. Hamrick
- KrokodileDandy
- Kunal Marwaha
- Matthew Seal
- Matthias Geier
- Miro Hrončok
- M Pacer
- Nils Japke
- njapke
- Sebastian Führ
- Sylvain Corlay
- Tyler Makaro
- Valery M
- Wayne Witzel

The full list of changes they made can be seen [on
GitHub](https://github.com/jupyter/nbconvert/issues?q=milestone%3A5.6+)

Significant Changes

Jupter Client Pin

The `jupyter_client` dependency is now pinned to `>5.3.1`. This is done
to support the Parallel NBConvert below, and
future versions may require interface changes from that version.

Parallel NBConvert

NBConvert `--execute` can now be run in parallel via threads,
multiprocessing, or async patterns! This means you can now parallelize
nbconvert via a bash loop, or a python concurrency pattern and it should
be able to execute those notebooks in parallel.

Kernels have varying support for safe concurrent execution. The ipython
kernel (ipykernel version 1.5.2 and higher) should be safe to run
concurrently using Python 3. However, the Python 2 ipykernel does not
always provide safe concurrent execution and sometimes fails with a
socket bind exception. Unlike ipykernel which is maintained by the
project, other community-maintained kernels may have varying support for
concurrent execution, and these kernels were not tested heavily.

Issues for nbconvert can be viewed here: [1018](https://github.com/jupyter/nbconvert/pull/1018), and [#1017](https://github.com/jupyter/nbconvert/pull/1017)

Execute Loop Rewrite

This release completely rewrote the execution loop responsible for
monitoring kernel messages until cell execution is completed. This
removes an error where kernel messages could be dropped if too many were
posted too quickly. Furthermore, the change means that messages are not
buffered. Now, messages can be logged immediately rather than waiting
for the cell to terminate.

See [994](https://github.com/jupyter/nbconvert/pull/994) for exact code changes if
you're curious.

Comprehensive notes

New Features

- Make a default global location for custom user templates
[1028](https://github.com/jupyter/nbconvert/pull/1028)
- Parallel execution improvements [1018](https://github.com/jupyter/nbconvert/pull/1018), and [#1017](https://github.com/jupyter/nbconvert/pull/1017)
- Added `store_history` option to `preprocess_cell` and `run_cell`
[1055](https://github.com/jupyter/nbconvert/pull/1055)
- Simplify the function signature for preprocess()
[1042](https://github.com/jupyter/nbconvert/pull/1042)
- Set flag to not always stop kernel execution on errors
[1040](https://github.com/jupyter/nbconvert/pull/1040)
- `setup_preprocessor` passes kwargs to `start_new_kernel`
[1021](https://github.com/jupyter/nbconvert/pull/1021)

Fixing Problems

- Very fast stream outputs no longer drop some messages
[994](https://github.com/jupyter/nbconvert/pull/994)
- LaTeX errors now properly raise exceptions [1053](https://github.com/jupyter/nbconvert/pull/1053)
- Improve template whitespacing [1076](https://github.com/jupyter/nbconvert/pull/1076)
- Fixes for character in LaTeX exports and filters
[1068](https://github.com/jupyter/nbconvert/pull/1068), [#1039](https://github.com/jupyter/nbconvert/pull/1039), [#1024](https://github.com/jupyter/nbconvert/pull/1024), and
[1077](https://github.com/jupyter/nbconvert/pull/1077)
- Mistune pinned in preparation for 2.0 release
[1074](https://github.com/jupyter/nbconvert/pull/1074)
- Require mock only on Python 2 [1060](https://github.com/jupyter/nbconvert/pull/1060) and [#1011](https://github.com/jupyter/nbconvert/pull/1011)
- Fix selection of mimetype when converting to HTML
[1036](https://github.com/jupyter/nbconvert/pull/1036)
- Correct a few typos [1029](https://github.com/jupyter/nbconvert/pull/1029)
- Update `export_from_notebook` names [1027](https://github.com/jupyter/nbconvert/pull/1027)
- Dedenting html in ExtractOutputPreprocessor [1023](https://github.com/jupyter/nbconvert/pull/1023)
- Fix backwards incompatibility with markdown2html
[1022](https://github.com/jupyter/nbconvert/pull/1022)
- Fixed html image tagging [1013](https://github.com/jupyter/nbconvert/pull/1013)
- Remove unnecessary css [1010](https://github.com/jupyter/nbconvert/pull/1010)

Testing, Docs, and Builds

- Pip-install nbconvert on readthedocs.org [1069](https://github.com/jupyter/nbconvert/pull/1069)
- Fix various doc build issues [1051](https://github.com/jupyter/nbconvert/pull/1051), [#1050](https://github.com/jupyter/nbconvert/pull/1050),
[1019](https://github.com/jupyter/nbconvert/pull/1019), and
[1048](https://github.com/jupyter/nbconvert/pull/1048)
- Add issue templates [1046](https://github.com/jupyter/nbconvert/pull/1046)
- Added instructions for bumping the version forward when releasing
[1034](https://github.com/jupyter/nbconvert/pull/1034)
- Fix Testing on Windows [1030](https://github.com/jupyter/nbconvert/pull/1030)
- Refactored `test_run_notebooks` [1015](https://github.com/jupyter/nbconvert/pull/1015)
- Fixed documentation typos [1009](https://github.com/jupyter/nbconvert/pull/1009)