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README.md

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-# spec
-Minimal shared API spec
+# Shared specifications for Python Visualization
+
+This repo will store any specifications that arise as well as any build and testing code that is determined to be useful for managing and verifying the use of specs.
+
+Every spec will have a version and target a specific section of the library API.

spec_01.md

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+- Spec: 1
+- Title: Methods on libraries
+- Version: 0.1
+- Last-Modified: 2019-07-19
+- Authors: [James Bednar](),
+           [Julia Signell]([email protected]),
+           [Jake Vanderplas]()
+- Status: Active
+- Type: Standards
+- Content-Type: text/markdown
+- Created: 2019-07-19
+
+## Abstract
+This spec describes a proposed minimal shared Python API for plotting libraries.
+
+This spec uses LIBRARY to refer to any specific visualization library.
+
+## If a method doesn't make sense
+If a given operation doesn't make sense for that library, then it can satisfy the spec by simply having that method return a message to that effect ("Unsupported: LIBRARY does not provide JSON output").
+
+## `.__pyviz_spec__()` method
+Calling `.__pyviz_spec__()` on the library should return a list of the specs that the library complies with. It should include the version of the spec that is being used.
+
+```python
+>>> LIBRARY.__pyviz_spec__()
+{1: 0.1, 2: 0.1}
+```
+
+## Enable output from library
+Each library should provide a uniform way to enable itself in jupyter notebook & jupyterlab.
+
+> #### What currently exists
+> - matplotlib has `%matplotlib inline`
+> - bokeh has `bokeh.output_notebook()`
+> - altair has `alt.renderers.enable('notebook')`
+> - holoviews has `hv.extension('bokeh')`
+> - hvplot has `import hvplot.pandas`
+
+### Proposal: function call
+Provide an `enable()` function call on the library that can take an optional `output` kwarg, but provides a sensible default.
+
+`LIBRARY.enable()` == `LIBRARY.enable(output='notebook')`
+
+**NOTE**: This spec doesn't cover the case where you are in a notebook and want to generate a figure separately from a notebook.
+
+#### Context
+A function call is preferred over magics because some tools need a specification that is usable both within and outside of jupyter. We can always add special cases to deal with magics, but prefer just to have a normal Python call that can register things with Jupyter if it's available but doesn't otherwise cause syntax errors (if not skipped) or missing functionality (if skipped) outside of Jupyter/IPython.

spec_02.md

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+- Spec: 2
+- Title: Methods on figure objects
+- Version: 0.1
+- Last-Modified: 2019-07-19
+- Authors: [James Bednar](),
+           [David Hoese](),
+           [Jon Mease]([email protected]),
+           [Julia Signell]([email protected]),
+- Status: Active
+- Type: Standards
+- Content-Type: text/markdown
+- Created: 2019-07-19
+
+## Abstract
+This spec describes a proposed shared Python API for accessing objects from various plotting libraries.
+
+In this notebook we will use **figure** to refer to any object that has a visible representation but that can also be saved, exported, etc. This includes generic visualizations or animations that may or may not be considered a "plot" with axes, ticks, and so on.```
+
+When detailing a method, this spec uses FIGURE to refer to any specific figure object and LIBRARY to refer to any specific visualization library.
+
+## If a method doesn't make sense
+If a given operation doesn't make sense for that library, then it can satisfy the spec by simply having that method return a message to that effect ("Unsupported: LIBRARY does not provide JSON output").
+
+## Jupyter methods
+Every library that supports rendering in Jupyter should support at least one of the various IPython rich display methods, i.e. `_repr_mimebundle_`, `_repr_html_`, `_repr_png_`, `_ipython_display_`.
+
+## `.show()`
+Every figure should have the ability to display itself.
+
+### Proposal
+ 1) The top-level figure class should have a `.show()` method that can be called without arguments to display the figure as a side-effect.
+ 2) The optional `output` kwarg can be used to override the current default renderer. e.g.:
+    - `FIGURE.show(output='png')` to display the figure as a static png image.
+    - `FIGURE.show(output='html')` to display the figure in a new browser tab. This works in both jupyter/IPython and non-jupyter/IPython contexts. If the library provides interactivity, an interactive figure is preferred.
+
+After this kwarg, `show` can have any additional kwargs needed.
+
+**NOTE**: When specifying options for `output`, `jpg` is preferred to `jpeg`.
+
+#### What to return
+`FIGURE.show()` should return `None`.
+
+## `.save()` method
+Every figure should have the knowledge of how to export itself to a file on disk.
+
+> #### What currently exists
+>  - matplotlib has `.savefig` which saves the current figure, with options `fname` and `format` among others.
+> - plotly has `write_*` methods which write the figure to a `file` (or writable object) and return `None`.
+> - bokeh has top level `export_*` methods for each output format as well as `save` (only outputs html) which both take a FIGURE as the arg.
+
+### Proposal
+Figures should have `FIGURE.save()` method for exporting.
+
+There are several kwargs that `save` should include:
+
+ 1) `file`: should be a file object or optionally a path to a file. If the LIBRARY does not support file paths and a user provides one rather than a file object, the LIBRARY should raise a sensible error. Can default to some user configured value.
+ 2) `output`: should be a file format that the figure can be exported to i.e. `'png'`, `'jpg'`, `'svg'`, `'json'`, `'html'`. The library should set a default output and/or allow the user to configure the output. For instance matplotlib does:
+    > If format is not set, then the output format is inferred from the extension of `fname`, if any, and from `rcParams["savefig.format"]` otherwise. If `format` is set, it determines the output format.
+    >
+    >from: [matplotlib.pyplot.savefig](https://matplotlib.org/3.1.1/api/_as_gen/matplotlib.pyplot.savefig.html)
+
+**NOTE**: These kwargs are deliberately selected to avoid builtins in python 3 which precludes `format`, but no longer precludes `file`.
+
+After these two, `save` can have any additional kwargs needed.
+
+**NOTE**: When specifying options for `output`, `jpg` is preferred to `jpeg`.
+
+#### What to return
+`FIGURE.save()` should return the file path or object that was saved to.
+
+#### Some examples
+Save to default location:
+
+```python
+FIGURE.save()
+```
+
+Save to a particular location:
+
+```python
+with open('/path/to/output.html', 'w') as file:
+    FIGURE.save(file)
+```
+
+is equivalent to
+
+```python
+FIGURE.save(file='/path/to/output.html')
+```
+
+is equivalent to
+
+```python
+FIGURE.save('/path/to/output.html', output='html')
+```