Kamil Kisiel already answered for this case. In general, triggers are a feature of Debian and Debian-derived distributions that let packages defer some tasks that need to be performed during installation. This is useful for tasks that are shared among several packages, like in Python's case, compiling the Python modules.
As a specific example of where triggers save time, some documentation systems (like man or info) generate an index for all such documents installed, so when you install or update a package, its installation script will update this index. But if you are installing several such packages, in the days before triggers, all of the packages would individually update the index even though it needs to be done only once, so the installation would take longer. But now these packages can contain the index update as a trigger action, so that it is only performed once per installation.
The python-support package byte-compiles Python modules in to .pyc files. Typically when you run the module as a user, you don't have write access to the directories where the byte-compiled versions are placed, so the system does it for you when the packages are installed. Essentially it runs the update-python-modules script.
Kamil Kisiel already answered for this case. In general, triggers are a feature of Debian and Debian-derived distributions that let packages defer some tasks that need to be performed during installation. This is useful for tasks that are shared among several packages, like in Python's case, compiling the Python modules.
As a specific example of where triggers save time, some documentation systems (like
manorinfo) generate an index for all such documents installed, so when you install or update a package, its installation script will update this index. But if you are installing several such packages, in the days before triggers, all of the packages would individually update the index even though it needs to be done only once, so the installation would take longer. But now these packages can contain the index update as a trigger action, so that it is only performed once per installation.The python-support package byte-compiles Python modules in to .pyc files. Typically when you run the module as a user, you don't have write access to the directories where the byte-compiled versions are placed, so the system does it for you when the packages are installed. Essentially it runs the update-python-modules script.