Slack Blocks API Python Wrapper

1.2.3 verified Mon Apr 27 auth: no python

Python wrapper for the Slack Blocks API, providing a fluent interface for constructing Block Kit messages. Current version 1.2.3 works with Python >= 3.8.1, released occasionally with minor updates. It aims to simplify building complex Slack message layouts.

pip install slackblocks

Common errors

error TypeError: Object of type SectionBlock is not JSON serializable ↓

cause Trying to serialize the Message object directly without calling its `build()` or using `**message`

fix

Use **message when passing to slack_sdk: client.chat_postMessage(**message). Or call message.build() to get a dict.

error ModuleNotFoundError: No module named 'slackblocks' ↓

cause slackblocks is not installed or installed in a different environment.

fix

Run pip install slackblocks in your active environment.

error KeyError: 'blocks' ↓

cause The Slack API requires a 'blocks' field in the payload, but Message without blocks may omit it.

fix

Always provide a blocks parameter when constructing Message, even if empty list: blocks=[].

Warnings

gotcha `Message` does not directly send requests; it only builds the payload. You must use an HTTP client (e.g., slack_sdk) to send. ↓

fix Use `client.chat_postMessage(**message)` where `message` is a SlackBlocks Message object.

gotcha Blocks must be passed as a list to `Message`; passing a single block without list wrapping will break. ↓

fix Always wrap blocks: `blocks=[SectionBlock(...)]` even if one block.

deprecated The `channel` parameter in `Message` may be deprecated in future versions; prefer passing channel when sending via the client. ↓

fix Omit channel from Message constructor and set it in the HTTP call: `client.chat_postMessage(channel="#general", **message)`.

gotcha Text in SectionBlock must be a string, not a dict; using Block Kit object syntax incorrectly may cause errors. ↓

fix Use plain strings: `SectionBlock(text="Hello")`. For rich text, use `mrkdwn=True` or similar parameters.

Imports

Message
```
from slackblocks import Message
```
Main entry point for creating Slack messages.
SectionBlock
```
from slackblocks import SectionBlock
```
Used to add section blocks to messages.
ImageBlock
```
from slackblocks import ImageBlock
```
Used to add image blocks.
DividerBlock
```
from slackblocks import DividerBlock
```
Used to add a divider line.
ContextBlock
```
from slackblocks import ContextBlock
```
Used to add context elements.

Quickstart

Construct a basic Slack message with a section and an image block, then send using slack_sdk.

import os
from slackblocks import Message, SectionBlock, ImageBlock

message = Message(
    channel="#general",
    text="Hello, world!",
    blocks=[
        SectionBlock(text="This is a section block"),
        ImageBlock(image_url="https://example.com/image.png", alt_text="Example Image")
    ]
)
# Send via slack_sdk or similar
from slack_sdk import WebClient
client = WebClient(token=os.environ.get("SLACK_TOKEN", ""))
response = client.chat_postMessage(**message)
print(response)