Re: [PATCH] ob-python: support header argument `:results file graphics'

[Liu Hui <liuhui1610@gmail.com>]

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Ihor Radchenko <yantar92@posteo.net> 于2023年7月4日周二 19:29写道：

> That said, your patch should still work fine even with these
> considerations. But we may need to sort out this undocumented behaviour.
> Probably, an error like in `org-babel-graphical-output-file' should be
> thrown by `org-babel-generate-file-param'.

Yes. The main concern is that some users may rely on the undocumented
behavior.


> What about
>
> #+begin_src python :file "test.png" :results graphics file
> import matplotlib.pyplot as plt
> plt.plot([1,2,3,4,5])
> plt.savefig('test.png')
> plt.plot([5,4,3,2,1])
> plt.show()
> #+end_src

OK, I think that it is better to turn off the feature by default and I
have updated the patch. Inspired by ob-R, some extra header arguments
are supported. Thanks.

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From 5f3fc8602c0eb1f6d0c072bd0c1a6bb883b8c9f9 Mon Sep 17 00:00:00 2001
From: Liu Hui <liuhui1610@gmail.com>
Date: Wed, 5 Jul 2023 12:48:36 +0800
Subject: [PATCH] ob-python: Graphics output enhancement

* lisp/ob-python.el (org-babel-python-graphics-output-function): New
variable.
(org-babel-execute:python): Allow to save graphics output with a
user-defined function when the result type is `file graphics'.
(org-babel-python-matplotlib-graphics-output): New helper function to
generate code to save matplotlib-based graphics.
---
 lisp/ob-python.el | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/lisp/ob-python.el b/lisp/ob-python.el
index 0e0539d7a..4c304f83b 100644
--- a/lisp/ob-python.el
+++ b/lisp/ob-python.el
@@ -62,6 +62,14 @@ (defcustom org-babel-python-None-to 'hline
   :package-version '(Org . "8.0")
   :type 'symbol)
 
+(defvar org-babel-python-graphics-output-function nil
+  "A function generating Python code for producing graphics output.
+Specifically, for src blocks with `:results file graphics' header
+argument, the code returned by the function will be appended to
+the end of the src block and should produce the graphics file.
+It can be set to `org-babel-python-matplotlib-graphics-output'
+for matplotlib-based graphics.")
+
 (defun org-babel-execute:python (body params)
   "Execute a block of Python code with Babel.
 This function is called by `org-babel-execute-src-block'."
@@ -72,6 +80,9 @@ (defun org-babel-execute:python (body params)
 		   (cdr (assq :session params))))
          (result-params (cdr (assq :result-params params)))
          (result-type (cdr (assq :result-type params)))
+         (graphics-file (and (member "graphics" result-params)
+                             (ignore-errors
+                               (org-babel-graphical-output-file params))))
 	 (return-val (when (eq result-type 'value)
 		       (cdr (assq :return params))))
 	 (preamble (cdr (assq :preamble params)))
@@ -81,6 +92,10 @@ (defun org-babel-execute:python (body params)
 	   (org-babel-expand-body:generic
 	    body params
 	    (org-babel-variable-assignments:python params))
+           (when graphics-file
+             (if (functionp org-babel-python-graphics-output-function)
+                 (funcall org-babel-python-graphics-output-function
+                          graphics-file params)))
 	   (when return-val
 	     (format (if session "\n%s" "\nreturn %s") return-val))))
          (result (org-babel-python-evaluate
@@ -149,6 +164,24 @@ (defun org-babel-python-table-or-string (results)
                 res)
       res)))
 
+(defun org-babel-python-matplotlib-graphics-output (out-file params)
+  "Return the Python code for saving graphics to `OUT-FILE'."
+  (let* ((allowed-args '(:dpi :format :backend))
+         (args (mapconcat
+	        (lambda (pair)
+		  (if (member (car pair) allowed-args)
+		      (format ",%s=%S"
+			      (substring (symbol-name (car pair)) 1)
+			      (cdr pair)) ""))
+	        params "")))
+    (format "
+import matplotlib.pyplot
+if len(matplotlib.pyplot.get_fignums()) > 0:
+    matplotlib.pyplot.gcf().savefig('%s'%s)
+else:
+    raise RuntimeWarning('No figure is found')"
+            out-file args)))
+
 (defvar org-babel-python-buffers '((:default . "*Python*")))
 
 (defun org-babel-python-session-buffer (session)
-- 
2.25.1