The Designated Initializer came up since the ISO C99 and is a different and more dynamic way to initialize in C when initializing struct, union or an array. The biggest difference to standard initialization is that you don't have to declare the elements in a fixed order and you can also omit element.
You would use a constructor without the help of an object initializer if the constructor sufficiently set the initial state of the object. An object initializer however must be used in conjunction with a constructor. The syntax requires the explicit or implicit use (VB.Net and C#) of a constructor to create the initial object.
Brace-or-equal-initializer must reside in a header file along with a class declaration. If both are combined, member-initializer-list takes priority over brace-or-equal-initializer (that is, brace-or-equal-initializer is ignored). (C++11 only, until C++14) A class that uses brace-or-equal-initializer violates constraints for an aggregate type.
I have heard that the init function in python is not a Constructor, It's an Initializer and actually the new function is the Constructor and the difference is that the init function is called after the creation of the object and the new called before.
The initialization rules of C Whenever initializing an array or struct, this must be done using an initializer list with the curly braces {}, aka "brace-enclosed list". The initializer rules work so that the compiler looks at the array or struct being initialized and starts with the first item. In case of arrays that is the object at index [0].
Naked (i.e., declared without initializers) variables local to a class or function. dynamically allocated instances. However, in other places (notably static variables) and in the case of anything given the empty initializer paramters (when that is valid), gets the default (zero) initialization.