Thanks for noting. :) I added that in my Emacs config now.

[stardiviner]           <Hack this world!>      GPG key ID: 47C32433
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On Tue, Nov 3, 2020 at 5:53 PM Sebastian Gimeno <changimeno@gmail.com>
wrote:

> Dear Stardiviner,
>
> I used the "scimax" configuration. Scimax's maintainer, John Kitchin,
> helped me out to find the root cause of the problem, i.e. the following
> addition to " python-font-lock-keywords":
>
> (setq python-font-lock-keywords
>       (append python-font-lock-keywords
>      '(;; this is the full string.
> ;; group 1 is the quote type and a closing quote is matched
> ;; group 2 is the string part
> (
> ;; "f\\(['\"]\\{1,3\\}\\)\\([^\\1]+?\\)\\1"
> "f\\(['\"]\\{1,3\\}\\)\\(.+?\\)\\1"
> ;; these are the {keywords}
> ("{[^}]*?}"
>  ;; Pre-match form
>  (progn (goto-char (match-beginning 0)) (match-end 0))
>  ;; Post-match form
>  (goto-char (match-end 0))
>  ;; face for this match
>  (0 font-lock-variable-name-face t))))))
>
> Commenting out this code snippet, the fontfying / HTML-export problem goes
> away.
>
> Cheers,
> sebastian
>
>
>
>
> On Tue, Nov 3, 2020 at 6:50 AM stardiviner <numbchild@gmail.com> wrote:
>
>> I have same problem sometimes in different babel languages.
>> I would like to know what caused this problem too.
>> Can you send me a message after you solved problem? Thanks in advance. :)
>> smile
>>
>> [stardiviner]           <Hack this world!>      GPG key ID: 47C32433
>> IRC(freeenode): stardiviner                     Twitter:  @numbchild
>> Key fingerprint = 9BAA 92BC CDDD B9EF 3B36  CB99 B8C4 B8E5 47C3 2433
>> Blog: http://stardiviner.github.io/
>>
>>
>> On Mon, Nov 2, 2020 at 2:26 AM Sebastian Gimeno <changimeno@gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> I am using emacs 27.1 and org-plus-contrib 20201026.
>>>
>>> I am having problems with the fontification of python and ipython
>>> source blocks when the code contains curly brackets "{}" (other course
>>> blocks are ok). For instance, the following snippet
>>>
>>> #+BEGIN_SRC python :results drawer
>>> import matplotlib.pyplot as plt
>>> plt.plot([1,2,3])
>>> plt.show()
>>> a=1
>>> print("a={}".format{a})
>>> #+END_SRC
>>>
>>> does not fontify correctly in either python or ipython source blocks.
>>>
>>> As a consequence, when exporting the org file to HTML (C-c C-e h h), it
>>> fails with the following message:
>>>
>>> font-lock-fontify-keywords-region: Invalid function: #<subr progn>
>>>
>>> If changing the code snippet to:
>>>
>>> #+BEGIN_SRC python :results drawer
>>> import matplotlib.pyplot as plt
>>> plt.plot([1,2,3])
>>> plt.show()
>>> a=1
>>> print("a=%s" % a)
>>> #+END_SRC
>>>
>>> the block fontifies and the file is exported to HTML correctly.
>>>
>>> Can you reproduce this behaviour?
>>>
>>> Many thanks in advance!
>>>
>>