Pox: Filesystem Utilities

Common errors

• ImportError: No module named pox.core

  cause This error often occurs when the POX library is not correctly installed as a Python package, or when there's a mismatch between the import statement and the actual directory structure, especially after cloning the repository directly. It can also stem from Python 2 vs. Python 3 compatibility issues, as older POX versions primarily supported Python 2.7.
  fix If installing via Git, ensure `__init__.py` files exist in relevant directories. If your project is a subdirectory of the cloned `pox` repository, you might need to adjust imports from `from pox.core import ...` to `from pox.pox.core import ...`. For modern `pox` (uqfoundation), ensure Python 3.9+ is used and install with `pip install pox`. For older `pox` (noxrepo), use Python 2.7.

• AttributeError: 'IPAddr' object has no attribute 'split'

  cause This error occurs when attempting to use string manipulation methods, such as `split()`, directly on an `IPAddr` object from `pox.lib.addresses`. The `IPAddr` object represents an IP address but is not a native Python string type.
  fix Convert the `IPAddr` object to its string representation first using the `.toStr()` method before applying string operations. For example, `st.toStr().split('.')` instead of `st.split('.')`.

• WARNING:version:Support for Python 3 is experimental.

  cause This warning indicates that you are likely running an older version of POX, which was originally developed for Python 2.7, with a Python 3 interpreter. While some functionality might work, core components or dependencies may not be fully compatible, leading to unexpected behavior or further errors.
  fix For older POX distributions (e.g., `noxrepo/pox`), use a Python 2.7 interpreter. If you intend to use POX with Python 3, ensure you are using the actively maintained `pox` library from the `uqfoundation` project, which supports Python 3.9+.

• AttributeError: 'YourControllerClass' object has no attribute 'connection'

  cause This `AttributeError` typically arises in POX when a custom controller component or module tries to access an attribute like `connection` directly from its own instance (`self.connection`), but `connection` is actually an attribute of an event object (e.g., `event.connection`) that is passed to event handler functions within the controller.
  fix Ensure that you are accessing the `connection` attribute from the `event` object provided to your event handler. For instance, if you have an `_handle_PacketIn` method, use `event.connection.send(fm)` instead of `self.connection.send(fm)`.

Warnings

• breaking Pox dropped formal support for Python 3.7.
  Fix: Ensure your Python environment is version 3.8 or higher when using pox>=0.3.4.
• breaking The minimum required Python version was increased from 3.7 to 3.8.
  Fix: Upgrade your Python installation to version 3.8 or newer. For earlier Python versions, use pox<0.3.6.
• breaking The minimum required Python version was further increased from 3.8 to 3.9.
  Fix: Upgrade your Python installation to version 3.9 or newer. For Python 3.8, use pox<0.3.7.
• breaking The `pox` module does not expose a `version()` method as part of its public API, leading to an `AttributeError` when `pox.version()` is called.
  Fix: To get the installed package version, use `importlib.metadata.version('pox')` (for Python 3.8+) or `pkg_resources.get_distribution('pox').version`. If `pox.version()` refers to a specific library function, consult the `pox` documentation for the correct API.
• breaking The `pox.version()` method is not available or has been removed from the `pox` library's API, leading to an `AttributeError`.
  Fix: Consult the `pox` library documentation for the current method of checking its version, or update your code to remove the call to `pox.version()`.

Install

• pip install pox Install Pox

Imports

• pox

  import pox

Quickstart

This quickstart demonstrates how to import the pox library and retrieve its version, license, and citation information.

import pox

# Get the library version
print(f"Pox Version: {pox.version()}")

# Display the license information
print("\n--- License ---")
print(pox.license())

# Display citation information
print("\n--- Citation ---")
print(pox.citation())