Python version deference

Question

In 2.7 can work with out any parentheses... In 3.x it's mandatory.... Switching versions complicated... Enlighten me please

Answer 1

For example, print was a statement in 2.x and a function in 3.x.

It was changed to make the operation more consistent with the rest of Python.

Here's the rationale:
https://www.python.org/dev/peps/pep-3105/