Fixing Py-clob-client MarketOrderArgs 'side' Error

by Sebastian Müller 51 views

Hey everyone! Today, we're diving into a common issue faced when using the py-clob-client library, specifically the MarketOrderArgs error where it throws an "unexpected keyword argument 'side'" exception. This can be frustrating, especially when you're following examples and feel like you've got everything right. So, let's break down the problem, understand why it happens, and explore how to fix it. We'll also touch on a potential documentation issue spotted in the examples. Let's get started!

Understanding the MarketOrderArgs Error

If you're encountering the "MarketOrderArgs.init() got an unexpected keyword argument 'side'" error, you're not alone. This typically arises when you're trying to create a market order using the MarketOrderArgs class in py-clob-client and include the side argument, which specifies whether you want to buy or sell.

Here’s a typical scenario where this error occurs:

from py_clob_client.order_builder.constants import SELL
from py_clob_client.order_builder import MarketOrderArgs, OrderArgs

# Example causing the error
order_args = MarketOrderArgs(
    token_id=token_id,
    amount=size,
    side=SELL,
)

The error message indicates that the MarketOrderArgs class constructor (__init__) doesn't recognize the side argument. This is puzzling because the OrderArgs class, used for limit orders, does accept the side argument. So, what’s the deal?

Why Does This Happen?

The root cause of this issue usually lies in the design of the py-clob-client library itself. Market orders, by definition, are executed immediately at the best available price. Therefore, the direction (buy or sell) is implicitly determined by the type of market order function you call (e.g., create_market_buy_order or create_market_sell_order).

In simpler terms, the MarketOrderArgs class is designed to only accept the essential parameters for a market order: token_id and amount. The side (buy or sell) is handled at a higher level, within the specific function you use to create the market order.

Dissecting the Code: MarketOrderArgs vs. OrderArgs

To truly grasp why this happens, let's compare the intended usage of MarketOrderArgs with OrderArgs:

  • MarketOrderArgs: This class is streamlined for market orders. You provide the token_id (the asset you want to trade) and the amount (how much you want to trade). The library infers the side from the specific function you call (create_market_buy_order or create_market_sell_order).
  • OrderArgs: This class is designed for limit orders. Limit orders require you to specify not only the token_id and amount but also the price at which you're willing to trade and the side (buy or sell). This is because limit orders are not executed immediately; they're placed on the order book and only filled if the price reaches your specified level.

This distinction highlights why MarketOrderArgs doesn't need a side argument – the function you use to create the order already implies the direction of the trade.

How to Fix the MarketOrderArgs Error

Now that we understand the root cause, let's get to the solution. The key is to remove the side argument from your MarketOrderArgs instantiation and use the appropriate function (create_market_buy_order or create_market_sell_order) provided by the py-clob-client.

Here’s the corrected approach:

from py_clob_client.order_builder import MarketOrderArgs

# Corrected example for a market sell order
order_args = MarketOrderArgs(
    token_id=token_id,
    amount=size,
)

signed_order = self.client.create_market_sell_order(order_args)
resp = self.client.post_order(signed_order)
return resp

# Corrected example for a market buy order
order_args = MarketOrderArgs(
    token_id=token_id,
    amount=size,
)

signed_order = self.client.create_market_buy_order(order_args)
resp = self.client.post_order(signed_order)
return resp

Notice that we've removed the side=SELL argument from MarketOrderArgs. Instead, we use self.client.create_market_sell_order() to create a sell order and self.client.create_market_buy_order() to create a buy order. This aligns with the intended design of the library and resolves the error.

Step-by-Step Solution

  1. Remove the side argument: When creating a MarketOrderArgs object, omit the side parameter.
  2. Use the correct function: Use self.client.create_market_sell_order() for selling and self.client.create_market_buy_order() for buying.
  3. Pass MarketOrderArgs: Pass the MarketOrderArgs object containing token_id and amount to the chosen function.

By following these steps, you'll successfully create market orders without encountering the "unexpected keyword argument 'side'" error.

Spotting and Addressing Documentation Issues

It's crucial to highlight the importance of accurate documentation and examples. In this case, the user pointed out a potential issue in the py-clob-client examples, specifically in the market_sell_order example, where it was mentioned as creating a buy order instead of a sell order. This kind of discrepancy can lead to confusion and errors.

The Importance of Correct Examples

Examples serve as a primary guide for developers learning a new library or framework. When examples contain errors or inconsistencies, it can lead to developers adopting incorrect patterns, resulting in bugs and wasted time. Therefore, maintaining accurate and up-to-date examples is essential for any project.

How to Contribute to Documentation

If you spot an error in documentation or an example, don't hesitate to contribute! Most open-source projects welcome contributions to their documentation. Here’s how you can typically help:

  1. Identify the issue: Clearly understand the error or inconsistency.
  2. Report the issue: If you're not sure how to fix it, create an issue on the project's repository (e.g., on GitHub) detailing the problem.
  3. Submit a pull request: If you know how to fix it, you can submit a pull request with the corrected documentation or example.

By contributing to documentation, you're helping other developers and improving the overall quality of the project. Your contributions are invaluable!

Best Practices for Using py-clob-client

To ensure a smooth experience with py-clob-client, here are some best practices to keep in mind:

  1. Understand Order Types: Clearly differentiate between market and limit orders. Market orders are executed immediately at the best available price, while limit orders are placed on the order book at a specific price.
  2. Use the Correct Functions: For market orders, use create_market_buy_order and create_market_sell_order. For limit orders, use create_order.
  3. Refer to Documentation: Always consult the official py-clob-client documentation for the most up-to-date information and examples.
  4. Test Thoroughly: Before deploying your code to a live environment, test your order creation and execution logic thoroughly in a test environment.
  5. Handle Errors: Implement proper error handling to catch and manage exceptions that may occur during order creation and execution.

By following these best practices, you'll minimize potential issues and build robust trading applications with py-clob-client.

Common Pitfalls and How to Avoid Them

Let's explore some common pitfalls developers encounter when working with py-clob-client and how to avoid them:

  1. Incorrect Argument Passing: One frequent mistake is passing the side argument to MarketOrderArgs. Remember, MarketOrderArgs only requires token_id and amount. The side is determined by the function you use (create_market_buy_order or create_market_sell_order).
  2. Mixing Up Order Types: Confusing market and limit orders can lead to unexpected behavior. Ensure you use the correct functions and argument classes for each order type.
  3. Not Handling Exceptions: Failing to handle exceptions can cause your application to crash or behave unpredictably. Implement try-except blocks to gracefully handle potential errors.
  4. Using Outdated Library Versions: Using an outdated version of py-clob-client may contain bugs or lack important features. Keep your library updated to the latest version to benefit from bug fixes and improvements.
  5. Ignoring Documentation: Neglecting to consult the documentation can lead to misunderstandings and incorrect usage. Always refer to the official documentation for accurate information.

By being aware of these common pitfalls and taking steps to avoid them, you'll significantly reduce the chances of encountering issues and improve the reliability of your trading applications.

Conclusion: Mastering Market Orders in py-clob-client

In this article, we've tackled the "unexpected keyword argument 'side'" error in MarketOrderArgs head-on. We've explored why this error occurs, how to fix it, and the importance of accurate documentation and examples. Remember, the key takeaway is that MarketOrderArgs doesn't require the side argument; the direction of the trade is determined by the function you call (create_market_buy_order or create_market_sell_order).

By understanding the nuances of py-clob-client and following best practices, you can confidently create market orders and build powerful trading applications. Don't forget to contribute to the project by reporting issues and suggesting improvements. Happy trading, guys!