org-get-priority-function

org-get-priority-function is a variable defined in `org.el'.
Its value is

nil

• This variable may be risky if used as a file-local variable.

Documentation:
Function to extract the priority from a string.
The string is normally the headline. If this is nil Org computes the
priority from the priority cookie like [#A] in the headline. It returns
an integer, increasing by 1000 for each priority level.
The user can set a different function here, which should take a string
as an argument and return the numeric priority.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.