We started using slack in our group this past year but only recently we started to realize the power of the slack APIs. Slack has given developers a very handy way to retrieve information or receive alerts via ‘bots’, that before slack we would either have to build a web app to view or receive alerts via email. One idea I had recently was to create a slack bot to send reminders about open pull requests in GitHub. This is a mini-tutorial about how to use python and slackclient (a slack client for python) to create some nicely formatted messages to send to slack chats.

Where to Start

If you’re new to writing slack bots, the best place to start is Bot Users on the slack API page. The two most important parts of this page are:

• Creating a new bot user integration
• Getting a bot access token

Assuming you’re on Python 2.7, getting python ready is pretty simple. Install the slackclient python package by using the following:

And now you should be ready to code!

Sending A Simple Message

Here is a simple example of setting up the client and sending a message. Keep in mind, when you have a bot in production, the Slack API token shouldn’t be stored in code. It will more than likely be set as an environment variable in each environment.

from slackclient import SlackClient

def send_bot_info():
    sc = SlackClient(SLACK_TOKEN)

    sc.api_call(
        'chat.postMessage',
        username='OpenPR Bot',
        channel='your-channel-name',
        text='Awesome, all set up'
    )

This sends a message to slack that looks like the following:

Sending A Message With An Attachment

But for my bot, I needed something with a little more information. I needed fields that contain various titles, a link, and a variable number of lines of text. This code is a bit long, but it can be explained simply in the picture below:

It should be noted that any number of lines can be concatenated in the ‘text’ area of the attachment. Don’t worry, if the amount of text gets too large, slack will shorten it and create a ‘show more’ button. Now here’s the code (note: You’ll need a way to get the SLACK_TOKEN into your code using whatever method needed).

from slackclient import SlackClient
import json

def main():
    sc = SlackClient(SLACK_TOKEN)

    slack_message = build_pr_message()

    sc.api_call(
        "chat.postMessage",
        username='OpenPR Bot',
        channel='bb-slackbot-test',
        text=slack_message['text'],
        attachments=json.dumps(slack_message['attachments'])
    )

# This builds the main text and attachment for the slack message.
def build_pr_message():
    message_dict = {}
    message_dict['text'] = "your_repo: Open PR 1 of 1"
    message_dict['attachments'] = build_pr_attachment()
    return message_dict


# This section of code creates the slack 'attachment' area. It is a dictionary
# to keep things simple.

def build_pr_attachment():
    attachment_dict = {}
    attachment_dict['pretext'] = "*Changing data access layer*"
    attachment_dict['title'] = "PR created by Bob"
    attachment_dict['color'] = '#33FF3f'
    attachment_dict['title_link'] = 'http://url.com'

    # This setting allows us to use markdown in text (to bold, italicize, etc.)
    attachment_dict['mrkdwn_in'] = ['text', 'pretext']

    # Starting the 'text' section of the attachment. There is a lot of concatenation
    # going on here.
    text = "*Mergeable without conflicts?* No\n"
    text += "*Latest build status:* Ok\n"


    text += "*Latest comment by Jill* \n"
    text += ">>>This code is great, keep it up!\n"

    attachment_dict["text"] = text

    # Since attachment is in a JSON-formatted list, I'll create a list here to return
    attachment_list = [attachment_dict]
    return attachment_list


if __name__ == "__main__":
    main()

And there it is, a multi-dimensional slack message!