In classes and objects when we use const keyword for a data member , we use constructor! I know that

Question

question is why only constructor ? why const is intialized only with help of constructor?
is there any other way
if no, why not?

Answer 1

It helps if you understand what const is and means.

const = constant.

https://www.vocabulary.com/dictionary/constant

-Think of something or someone that does not change as constant-

A constant value has to be initialised with a value at the time of its creation because its value is constant and does not change.

To answer your question though:
You could set a const data members value with a hard coded value instead of setting it at initialisation, but that reduces flexibility.

Here is an example
https://code.sololearn.com/cbC2UcKGrXeF/?ref=app