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eval

Python expression evaluation commands for administrative use.

This module provides dangerous but powerful evaluation capabilities for bot owners and authorized sysadmins. It allows executing Python code in the context of the bot, with access to bot internals, Discord.py objects, and the current command context.

The eval command is restricted to bot owners by default, with optional sysadmin access. All eval operations are logged for security auditing.

Classes:

  • Eval –

    Discord cog for Python expression evaluation commands.

Functions:

  • insert_returns –

    Insert return statements into the body of the function definition.

  • setup –

    Set up the Eval cog.

Classes

Eval

Python
Eval(bot: Tux)

Bases: BaseCog

Discord cog for Python expression evaluation commands.

Provides the eval command which allows bot owners and authorized sysadmins to execute Python code in the context of the running bot. This is extremely powerful and potentially dangerous, so access is heavily restricted.

The eval command supports both synchronous and asynchronous Python code, with automatic return statement insertion for expression evaluation.

Initialize the Eval cog.

Parameters:

  • bot (Tux) –

    The bot instance to attach this cog to.

Methods:

  • eval –

    Evaluate a Python expression. (Owner only).

  • get_config –

    Get a configuration value from CONFIG with support for nested keys.

  • __repr__ –

    Return a string representation of the cog instance.

  • unload_if_missing_config –

    Check if required configuration is missing and log warning.

Attributes:

Attributes

db property
Python
db: DatabaseCoordinator

Get the database coordinator for accessing database controllers.

Returns:

  • DatabaseCoordinator –

    Coordinator providing access to all database controllers.

Examples:

Python Console Session
>>> await self.db.guild_config.get_guild_config(guild_id)
>>> await self.db.cases.create_case(...)
Notes

This property provides convenient access to database operations without needing to access self.bot.db directly.

Functions

eval async
Python
eval(ctx: Context[Tux], *, expression: str) -> None

Evaluate a Python expression. (Owner only).

Parameters:

  • ctx (Context[Tux]) –

    The context in which the command is being invoked.

  • expression (str) –

    The Python expression to evaluate.

_setup_command_usage
Python
_setup_command_usage() -> None

Generate usage strings for all commands in this cog that lack explicit usage.

The generated usage follows the pattern: <qualified_name> <param tokens>

Where: - Required parameters are denoted as <name: Type> - Optional parameters are denoted as [name: Type] - The prefix is intentionally omitted (provided by ctx.prefix)

Examples:

ban <member: Member> [reason: str] config set <key: str> <value: str>

Notes

Respects explicit usage strings if already set on a command. Errors during generation are logged but don't prevent cog loading.

_generate_usage
Python
_generate_usage(command: Command[Any, ..., Any]) -> str

Generate a usage string with support for flags and positional parameters.

This method inspects the command's callback signature to detect: - FlagConverter parameters (e.g., --flag value) - Positional parameters (e.g., <required> or [optional])

Parameters:

  • command (Command) –

    The command to generate usage for.

Returns:

  • str –

    Generated usage string, or qualified command name as fallback.

Notes

Delegates to shared usage generator for consistency across all cogs. Falls back gracefully to command name if generation fails.

get_config
Python
get_config(key: str, default: Any = None) -> Any

Get a configuration value from CONFIG with support for nested keys.

Parameters:

  • key (str) –

    The configuration key to retrieve. Supports dot notation for nested values (e.g., "BOT_INFO.BOT_NAME").

  • default (Any, default: None ) –

    Default value to return if key is not found, by default None.

Returns:

  • Any –

    The configuration value or default if not found.

Examples:

Python Console Session
>>> self.get_config("BOT_INFO.BOT_NAME")
'Tux'
>>> self.get_config("MISSING_KEY", "fallback")
'fallback'
Notes

Errors during retrieval are logged but don't raise exceptions. Returns the default value on any error.

__repr__
Python
__repr__() -> str

Return a string representation of the cog instance.

Returns:

  • str –

    String representation in format <CogName bot=BotUser>.

unload_if_missing_config
Python
unload_if_missing_config(condition: bool, config_name: str) -> bool

Check if required configuration is missing and log warning.

This allows cogs to detect missing configuration at load time and return early from init to prevent partial initialization.

Parameters:

  • condition (bool) –

    True if config is missing (should unload), False otherwise.

  • config_name (str) –

    Name of the missing configuration for logging purposes.

Returns:

  • bool –

    True if config is missing (caller should return early), False if config is present.

Examples:

Python Console Session
>>> def __init__(self, bot: Tux):
...     super().__init__(bot)
...     if self.unload_if_missing_config(not CONFIG.GITHUB_TOKEN, "GITHUB_TOKEN"):
...         return  # Exit early, cog will be partially loaded but won't register commands
...     self.github_client = GitHubClient()
Notes

When this returns True, the cog's init should return early to avoid initializing services that depend on the missing config. The cog will be loaded but commands won't be registered properly, preventing runtime errors.

For complete cog unloading, the bot owner should remove the cog from the modules directory or use the reload system to unload it programmatically.

_unload_self async
Python
_unload_self(extension_name: str) -> None

Perform the actual cog unload operation.

Parameters:

  • extension_name (str) –

    Full extension name to unload.

Notes

This is called as a background task by unload_if_missing_config(). Errors during unload are logged but don't raise exceptions.

Functions

insert_returns

Python
insert_returns(body: list[stmt]) -> None

Insert return statements into the body of the function definition.

Parameters:

  • body (list[stmt]) –

    The body of the function definition.

setup async

Python
setup(bot: Tux) -> None

Set up the Eval cog.

Parameters:

  • bot (Tux) –

    The bot instance to add the cog to.