Is there a way to download a setup file for macOS Sierra on Windows computer and then install later on my mac os For a long time I avoided upgrading to macOS Sierra, reason being my slow home internet connection. At my home, it predicts to take something like 1 day 2 hrs. 

On the other hand, my workplace internet speed is very fast. So I was thinking of downloading the Sierra setup file at my workplace and then verifying the installation media (if there is a way for verifying mac os because Xcode does have a way of verifying) and install it on my MacBook Pro. Only problem being my workplace computers have Windows operating system. So is there a way to download the setup file for macOS on Windows? I tried searching on Developer downloads and Support downloads but the only thing  I could find there were just updates and no main setup file.
There is probably no legal way to download macOS Sierra on a Windows PC. Non-legal ways (it depends on your country jurisdiction) are either macOS Sierra torrents or a macOS VM transferred to your PC (which requires some type 2 hypervisor like VMware Workstation or VirtualBox) to download the Sierra installer from within the macOS VM.

But: since you own a MacBook Pro, why don't you simply take it to your workplace and download macOS Sierra there?