In code like zip(*x) or f(**k), what do the * and ** respectively mean? How does Python implement that behaviour, and what are the performance implications?

_{See also: Expanding tuples into arguments. Please use that one to close questions where OP needs to use * on an argument and doesn't know it exists.}

_{See What does ** (double star/asterisk) and * (star/asterisk) do for parameters? for the complementary question about parameters.}

In code like zip(*x) or f(**k), what do the * and ** respectively mean? How does Python implement that behaviour, and what are the performance implications?

_{See also: Expanding tuples into arguments. Please use that one to close questions where OP needs to use * on an argument and doesn't know it exists. Similarly, use Converting Python dict to kwargs? for the case of using **.}

_{See What does ** (double star/asterisk) and * (star/asterisk) do for parameters? for the complementary question about parameters.}

In code like zip(*x) or f(**k), what do the * and ** respectively mean? How does Python implement that behaviour, and what are the performance implications?

_{See also: Expanding tuples into arguments. Please use that one to close questions where OP needs to use * on an argument and doesn't know it exists.}

In code like zip(*x) or f(**k), what do the * and ** respectively mean? How does Python implement that behaviour, and what are the performance implications?

_{See also: Expanding tuples into arguments. Please use that one to close questions where OP needs to use * on an argument and doesn't know it exists.}

_{See What does ** (double star/asterisk) and * (star/asterisk) do for parameters? for the complementary question about parameters.}

What does the * operator mean in Python, such as in code like zip(*x) or f(**k)?

1. How is it handled internally in the interpreter?
2. Does it affect performance at all? Is it fast or slow?
3. When is it useful and when is it not?
4. Should it be used in a function declaration or in a call?

In code like zip(*x) or f(**k), what do the * and ** respectively mean? How does Python implement that behaviour, and what are the performance implications?

_{See also: Expanding tuples into arguments. Please use that one to close questions where OP needs to use * on an argument and doesn't know it exists.}