Sublime text 3 not building a python file

Question

I am trying to build (Ctrl+B) a python (2.7 or 3) file in sublime text 3 in Ubuntu and I am expecting it to show some message at the bottom like

[ Finished in 1.2 s ]

But it is showing nothing. I even reinstalled the sublime text after completely removing it but it still is not working. I tried to make a new build system for Python3 but building with that too shows nothing. Here is the build system I have (Python3)

{
    "shell_cmd": "/usr/bin/env python3 ${file}",
    "selector": "source.python",
    "file_regex": "^(...*?):([0-9]*):?([0-9]*)",
    "working_dir": "${file_path}"
}

Other build systems which I have like for c++11 are working fine. Also I can use python2.7 as well as python3 in my terminal.

Answer 1

This answer was posted as an edit to the question Sublime text 3 not building a python file by the OP Sunil Kumar under CC BY-SA 3.0.

Thanks to @math2001's comment I realized that first line in my codes were user input and so it was waiting for user to type the input.