$ sudo apt-get update
$ sudo apt-get install python-singledispatch 

python-singledispatch is installed in your system.

Make ensure the python-singledispatch package were installed using the commands given below,

$ sudo dpkg-query -l | grep python-singledispatch *

You will get with python-singledispatch package name, version, architecture and description in a table

python-singledispatch package basic information: