How to obtain the number of correct symbols?

[97morningstar]

I would like to normalize the output following the article by Rafael C. Carrasco:

https://sites.google.com/site/textdigitisation/qualitymeasures/computingerrorrates

Like this:

where C = Number of correct characters

How can I calculate the number of correct characters?

[nabilafathia]

I have this issue as well and can't find the solution anywhere

[365id-github-admin]

Any more information in this matter?

[eslambakr]

I used the following lib instead: https://pypi.org/project/cer/1.0.1/