BlockKit for Python

Build beautiful Slack UIs fast. Fluent API with type hints, validation, and zero
dependencies.

shell
pip install blockkit

Here's the thing

Building Slack apps shouldn't feel like writing JSON by hand. It's tedious. It's
error prone. And honestly? It's a waste of your time.

You know what you want to build. Your editor should help you build it. That's
what BlockKit for Python does.

Before

This is what you're probably doing now:

python
# Building a simple approval message. What could go wrong?
message = {
    "blocks": [{
        "type": "section",
        "text": {
            "type": "mrkdwn",  # 🤔 or was it "markdown"?
            "text": "Please approve *Alice's* expense report for $42"
        },
        "accessory": {
            "type": "button",
            "text": {
                "type": "plain_text",  # 😕 wait, why can't buttons use mrkdwn?
                "text": "Approve"      # 🤞 hope this isn't too long
            },
            "action_id": "approve_button",
            "style": "green",  # ❌ is it "green"? "success"? "primary"?
            "confirm": {       # 🤔 what's the structure again?
                "title": {
                    "type": "plain_text",
                    "text": "Are you sure?"
                },
                "text": {
                    "type": "plain_text",
                    "text": "This action cannot be undone"
                },
                "confirm": {
                    "type": "plain_text",
                    "text": "Yes, approve"
                }
                # ❌ forgot the required "deny" field
            }
        }
    }],
    "thread_ts": 1234567890  # ❌ wait, should this be a string?
}

# Three bugs. Deeply nested JSON. Good luck debugging this.

Nest some JSON. Guess field names. Cross your fingers. Test it. Get an error.
Try again. Sound familiar?

After

Here's the same thing:

python
from blockkit import Message, Section, Button, Confirm

message = (
    Message()
    .add_block(
        Section("Please approve *Alice's* expense report for $42")  # ✅ Markdown detected automatically
        .accessory(
            Button("Approve")
            .action_id("approve_button")
            .style(Button.PRIMARY)  # ✅ Class constants prevent typos
            .confirm(
                Confirm()
                .title("Are you sure?")
                .text("This action cannot be undone")
                .confirm("Yes, approve")
                .deny("Cancel")  # ✅ Can't forget required fields
            )
        )
    )
    .thread_ts(1234567890)  # ✅ Converts types automatically
    .build()  # ✅ Validates everything: types, lengths, required fields
)

# Clean. Readable. BlockKit catches errors before you event send it to Slack.

Done. No guessing. No runtime surprises. Your editor helped you write it.

The difference

The library knows Slack's rules, so you don't have to memorize them. Your editor
autocompletes everything. Validation happens immediately.

When something's wrong, you'll know right away - not after deploying.

Real example

Let's build something real. An approval flow:

python
from blockkit import Modal, Section, Input, PlainTextInput, RadioButtons, Option

modal = (
    Modal()
    .title("Expense Approval")
    .add_block(Section("*New expense request from Alice*"))
    .add_block(
        Input("Amount").element(
            PlainTextInput().initial_value("$42.00").action_id("amount")
        )
    )
    .add_block(
        Input("Decision").element(
            RadioButtons()
            .add_option(Option("Approve ✅", "approve"))
            .add_option(Option("Reject ❌", "reject"))
            .action_id("decision")
        )
    )
    .submit("Submit")
    .build()
)