First, create a way to have your development and production servers pull settings from different files, say dev.py and prod.py. There are lots of ways to do this.
Then, create a setting, GOOGLE_ANALYTICS_KEY. In dev.py set it to the empty string. In prod.py, set it to your key, something like “UA-124465-1”. Create a context processor to add this setting to all your template contexts, either as GOOGLE_ANALYTICS_KEY, or just go ahead and add your settings module. Then, in your template, use it to conditionally include your analytics code:
{% if settings.GOOGLE_ANALYTICS_KEY %}
<script> blah blah {{settings.GOOGLE_ANALYTICS_KEY}} blah blah </script>
{% endif %}