PostHog Python

Official PostHog Python library to capture and send events to any PostHog instance (including PostHog.com).

This library uses an internal queue to make calls non-blocking and fast. It also batches requests and flushes asynchronously, making it perfect to use in any part of your web app or other server side application that needs performance.

Installation

pip install posthog

In your app, import the posthog library and set your api key before making any calls.

import posthog

posthog.api_key = 'YOUR API KEY'

You can find your key in the /setup page in PostHog.

To debug, you can set debug mode.

posthog.debug = True

Making calls

Capture

Capture allows you to capture anything a user does within your system, which you can later use in PostHog to find patterns in usage, work out which features to improve or where people are giving up.

A capture call requires

• distinct id which uniquely identifies your user
• event name to make sure
  • We recommend using [verb] [noun], like movie played or movie updated to easily identify what your events mean later on.

Optionally you can submit

• properties, which can be a dict with any information you'd like to add

For example:

posthog.capture('distinct id', 'movie played', {'movie_id': '123', 'category': 'romcom'})

Identify

Identify lets you add metadata on your users so you can more easily identify who they are in PostHog, and even do things like segment users by these properties.

An identify call requires

• distinct id which uniquely identifies your user
• properties with a dict with any key: value pairs

For example:

posthog.identify('distinct id', {
    'email': '[email protected]',
    'name': 'Dwayne Johnson'
})

The most obvious place to make this call is whenever a user signs up, or when they update their information.

Alias

To marry up whatever a user does before they sign up or log in with what they do after you need to make an alias call. This will allow you to answer questions like "Which marketing channels leads to users churning after a month?" or "What do users do on our website before signing up?"

In a purely back-end implementation, this means whenever an anonymous user does something, you'll want to send a session ID (Django, Flask) with the capture call. Then, when that users signs up, you want to do an alias call with the session ID and the newly created user ID.

The same concept applies for when a user logs in.

If you're using PostHog in the front-end and back-end, doing the identify call in the frontend will be enough.

An alias call requires

• previous distinct id the unique ID of the user before
• distinct id the current unique id

For example:

posthog.alias('anonymous session id', 'distinct id')

Django

For Django, you can do the initialisation of the key in the AppConfig, so that it's available everywhere.

in yourapp/apps.py

from django.apps import AppConfig
import posthog

class YourAppConfig(AppConfig):
    def ready(self):
        posthog.api_key = 'your key'

Then, anywhere else in your app you can do

import posthog

def homepage(request):
    # example capture
    posthog.capture(request.session.session_key, 'page view', ....)

Development

Naming confusion

As our open source project PostHog shares the same module name, we create a special posthog-analytics package, mostly for internal use to avoid module collision. It is the exact same.

How to release

1. Increase VERSION in posthog/version.py
2. run make release and make release_analytics
3. git commit -am "Release X.Y.Z." (where X.Y.Z is the new version)
4. git tag -a X.Y.Z -m "Version X.Y.Z" (where X.Y.Z is the new version).

Thank you

This library is largely based on the analytics-python package.