python-debug.sublime-snippet

<snippet>
    <content><![CDATA[import ipdb;ipdb.set_trace()]]></content>
    <!-- Optional: Tab trigger to activate the snippet -->
    <tabTrigger>ipdb</tabTrigger>
    <!-- Optional: Scope the tab trigger will be active in -->
    <scope>source.python</scope>
    <!-- Optional: Description to show in the menu -->
    <description>Import IPython debugger</description>
</snippet>

Place it in ~/Library/Application Support/Sublime Text 3/Packages/User