Invoking python under CygWin on Windows hangs

Try this

python -i

and yes you will find some glitches here and there !!!

Option -i forces an interactive prompt as shown in Python help python -h page here.

$ python -h
-i  : inspect interactively after running script; 
      forces a prompt even if stdin does not appear to be a terminal;
      also PYTHONINSPECT=x

The problem is that due to the way that the Cygwin terminal (MinTTY) behaves, the native Windows build of Python doesn't realize that stdout is a terminal device -- it thinks it's a pipe, so it runs in non-interactive mode instead of interactive mode, and it fully buffers its output instead of line-buffering it.

The reason that this is new is likely because in your previous Cygwin installation, you didn't have MinTTY, and the terminal used was just the standard Windows terminal.

In order to fix this, you either need to run Python from a regular Windows terminal (Cmd.exe), or install the Cygwin version of Python instead of a native Windows build of Python. The Cygwin version (installable as a package via Cygwin's setup.exe) understands Cygwin terminals and acts appropriately when run through MinTTY.

If the particular version of Python you want is not available as a Cygwin package, then you can also download the source code of Python and build it yourself under Cygwin. You'll need a Cygwin compiler toolchain if you don't already have one (GCC), but then I believe it should compile with a standard ./configure && make && make install command.