How to specify flask's validation method?

Question

Flask

Hello everyone
Tell me, who knows how to specify the validation method, in which only certain characters will be valid? I did not find any specifics on this issue in the documentation (I only found the presence of the entered values ​​and the number of characters ... although I may have missed / looked in the wrong place).
That is, for example, I have a form on my site that needs to be saved in the database. But the characters must be numbers \ Latin (small + large).
Thanks

Answer 1

stackoverflow.com/questions/25533370/regex-validat...

Answer 2

regular expressions