This provides a reticulate engine for knitr, suitable for usage when
attempting to render Python chunks. Using this engine allows for shared state
between Python chunks in a document -- that is, variables defined by one
Python chunk can be used by later Python chunks.
eng_python(options)Chunk options, as provided by knitr during chunk execution.
For most options, reticulate's python engine behaves the same as the default R engine included in knitr, but they might not support all the same features. Options in italic are equivalent to knitr, but with modified behavior.
eval (TRUE, logical): If TRUE, all expressions in the chunk are evaluated. If FALSE,
no expression is evaluated. Unlike knitr's R engine, it doesn't support numeric
values indicating the expressions to evaluate.
echo (TRUE, logical): Whether to display the source code in the output document. Unlike
knitr's R engine, it doesn't support numeric values indicating the expressions
to display.
results ('markup', character): Controls how to display the text results. Note that this option only
applies to normal text output (not warnings, messages, or errors). The behavior
should be identical to knitr's R engine.
collapse (FALSE, logical): Whether to, if possible, collapse all the source and output blocks
from one code chunk into a single block (by default, they are written to separate blocks).
This option only applies to Markdown documents.
error (TRUE, logical): Whether to preserve errors. If FALSE evaluation stops
on errors. (Note that RMarkdown sets it to FALSE).
warning (TRUE, logical): Whether to preserve warnings in the output. If FALSE, all warnings
will be suppressed. Doesn't support indices.
include (TRUE, logical): Whether to include the chunk output in the output document.
If FALSE, nothing will be written into the output document, but the code is still
evaluated and plot files are generated if there are any plots in the chunk, so you
can manually insert figures later.
dev: The graphical device to generate plot files. See knitr documentation for
additional information.
base.dir (NULL; character): An absolute directory under which the plots
are generated.
strip.white (TRUE; logical): Whether to remove blank lines in the beginning
or end of a source code block in the output.
dpi (72; numeric): The DPI (dots per inch) for bitmap devices (dpi * inches = pixels).
fig.width, fig.height (both are 7; numeric): Width and height of the plot
(in inches), to be used in the graphics device.
label: The chunk label for each chunk is assumed to be unique within the
document. This is especially important for cache and plot filenames, because
these filenames are based on chunk labels. Chunks without labels will be
assigned labels like unnamed-chunk-i, where i is an incremental number.
jupyter_compat (FALSE, logical): If TRUE then, like in Jupyter notebooks,
only the last expression in the chunk is printed to the output.
out.width.px, out.height.px (810, 400, both integers): Width and
height of the plot in the output document, which can be different with its
physical fig.width and fig.height, i.e., plots can be scaled in the output
document. Unlike knitr's out.width, this is always set in pixels.
altair.fig.width, altair.fig.height: If set, is used instead of
out.width.px and out.height.px when writing Altair charts.
The engine can be activated by setting (for example)
knitr::knit_engines$set(python = reticulate::eng_python)
Typically, this will be set within a document's setup chunk, or by the
environment requesting that Python chunks be processed by this engine.
Note that knitr (since version 1.18) will use the reticulate engine by
default when executing Python chunks within an R Markdown document.