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!
>