When we use package's begin part?

Question

Guys, I would like to learn when we use this part of package. I mean, because begin part only executes ones and never executes again in that session. So why we use this part?
create or replace
package body my_pack
is
  num number;
  str varchar2(50);
begin
  So when should we use this part of packages?????
  dbms_output.put_line(Why we use this part??????');
end;Thanks

Answer 1

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So in the example above of a logging interface, if another package also use the same interface then it will overwrite the verbosity level of the initial package that was loaded. In such a case, each procedure in a package will need to first set the log level prior to using application logging.
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That sounds like a design and implementation issue - not the way I implement logging. It doesn't make sense to have each package potentially overwrite the global log level like this. A package would either use the global log level already set or use it's own level.
The logging package would have an 'init' section that checks for a context variable to set the logging level and then either uses it or a default value if none is set. The log procedures would also be overloaded so that if no log level was specified as a parameter then the global value (set by the log package init section) would be used. The overloaded procedure would accept a log level parameter so that different levels could be used as needed.
The 'init' section in other packages would also check for a context variable (one for their package) and use it if it had been set. Otherwise they would get their log level from the value already set by the log package. If this 'other' package was the first to call the log package then they would get the value set by the log package 'init' as explained.