ContextExpression - AG2

ContextExpression

``autogen.ContextExpression`dataclass`

ContextExpression(expression)

A class to evaluate logical expressions using context variables.

Args:

expression (str): A string containing a logical expression with context variable references.

- Variable references use ${var_name} syntax: ${logged_in}, ${attempts}

- String literals can use normal quotes: 'hello', "world"

- Supported operators:

- Logical: not/!, and/&, or/|

- Comparison: >, <, >=, <=, ==, !=

- Supported functions:

- len(${var_name}): Gets the length of a list, string, or other collection

- Parentheses can be used for grouping

- Examples:

- "not ${logged_in} and ${is_admin} or ${guest_checkout}"

- "!${logged_in} & ${is_admin} | ${guest_checkout}"

- "len(${orders}) > 0 & ${user_active}"

- "len(${cart_items}) == 0 | ${checkout_started}"

Raises:

SyntaxError: If the expression cannot be parsed

ValueError: If the expression contains disallowed operations

``expression`instance-attribute`

expression

`evaluate`

evaluate(context_variables)

Evaluate the expression using the provided context variables.

PARAMETER	DESCRIPTION
`context_variables`	Dictionary of context variables to use for evaluation TYPE:`ContextVariables`

RETURNS	DESCRIPTION
`bool`	The result of evaluating the expression TYPE:`bool`

RAISES	DESCRIPTION
`KeyError`	If a variable referenced in the expression is not found in the context

Source code in autogen/agentchat/group/context_expression.py

157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 def evaluate(self, context_variables: ContextVariables) -> bool: """Evaluate the expression using the provided context variables. Args: context_variables: Dictionary of context variables to use for evaluation Returns: bool: The result of evaluating the expression Raises: KeyError: If a variable referenced in the expression is not found in the context """ # Create a modified expression that we can safely evaluate eval_expr = self._python_expr # Use the Python-syntax version # First, handle len() functions with variable references inside len_pattern = r"len$\${([^}]*)}$" len_matches = list(re.finditer(len_pattern, eval_expr)) # Process all len() operations first for match in len_matches: var_name = match.group(1) # Check if variable exists in context, raise KeyError if not if not context_variables.contains(var_name): raise KeyError(f"Missing context variable: '{var_name}'") var_value = context_variables.get(var_name) # Calculate the length - works for lists, strings, dictionaries, etc. try: length_value = len(var_value) # type: ignore[arg-type] except TypeError: # If the value doesn't support len(), treat as 0 length_value = 0 # Replace the len() expression with the actual length full_match = match.group(0) eval_expr = eval_expr.replace(full_match, str(length_value)) # Then replace remaining variable references with their values for var_name in self._variable_names: # Skip variables that were already processed in len() expressions if any(m.group(1) == var_name for m in len_matches): continue # Check if variable exists in context, raise KeyError if not if not context_variables.contains(var_name): raise KeyError(f"Missing context variable: '{var_name}'") # Get the value from context var_value = context_variables.get(var_name) # Format the value appropriately based on its type if isinstance(var_value, (bool, int, float)): formatted_value = str(var_value) elif isinstance(var_value, str): formatted_value = f"'{var_value}'" # Quote strings elif isinstance(var_value, (list, dict, tuple)): # For collections, convert to their boolean evaluation formatted_value = str(bool(var_value)) else: formatted_value = str(var_value) # Replace the variable reference with the formatted value eval_expr = eval_expr.replace(f"${{{var_name}}}", formatted_value) try: return eval(eval_expr) # type: ignore[no-any-return] except Exception as e: raise ValueError( f"Error evaluating expression '{self.expression}' (are you sure you're using ${{my_context_variable_key}}): {str(e)}" )


<br>157<br>158<br>159<br>160<br>161<br>162<br>163<br>164<br>165<br>166<br>167<br>168<br>169<br>170<br>171<br>172<br>173<br>174<br>175<br>176<br>177<br>178<br>179<br>180<br>181<br>182<br>183<br>184<br>185<br>186<br>187<br>188<br>189<br>190<br>191<br>192<br>193<br>194<br>195<br>196<br>197<br>198<br>199<br>200<br>201<br>202<br>203<br>204<br>205<br>206<br>207<br>208<br>209<br>210<br>211<br>212<br>213<br>214<br>215<br>216<br>217<br>218<br>219<br>220<br>221<br>222<br>223<br>224<br>225<br>226<br>227<br>228<br>	<br>def evaluate(self, context_variables: ContextVariables) -> bool:<br> """Evaluate the expression using the provided context variables.<br> Args:<br> context_variables: Dictionary of context variables to use for evaluation<br> Returns:<br> bool: The result of evaluating the expression<br> Raises:<br> KeyError: If a variable referenced in the expression is not found in the context<br> """<br> # Create a modified expression that we can safely evaluate<br> eval_expr = self._python_expr # Use the Python-syntax version<br> # First, handle len() functions with variable references inside<br> len_pattern = r"len\(\${([^}]*)}\)"<br> len_matches = list(re.finditer(len_pattern, eval_expr))<br> # Process all len() operations first<br> for match in len_matches:<br> var_name = match.group(1)<br> # Check if variable exists in context, raise KeyError if not<br> if not context_variables.contains(var_name):<br> raise KeyError(f"Missing context variable: '{var_name}'")<br> var_value = context_variables.get(var_name)<br> # Calculate the length - works for lists, strings, dictionaries, etc.<br> try:<br> length_value = len(var_value) # type: ignore[arg-type]<br> except TypeError:<br> # If the value doesn't support len(), treat as 0<br> length_value = 0<br> # Replace the len() expression with the actual length<br> full_match = match.group(0)<br> eval_expr = eval_expr.replace(full_match, str(length_value))<br> # Then replace remaining variable references with their values<br> for var_name in self._variable_names:<br> # Skip variables that were already processed in len() expressions<br> if any(m.group(1) == var_name for m in len_matches):<br> continue<br> # Check if variable exists in context, raise KeyError if not<br> if not context_variables.contains(var_name):<br> raise KeyError(f"Missing context variable: '{var_name}'")<br> # Get the value from context<br> var_value = context_variables.get(var_name)<br> # Format the value appropriately based on its type<br> if isinstance(var_value, (bool, int, float)):<br> formatted_value = str(var_value)<br> elif isinstance(var_value, str):<br> formatted_value = f"'{var_value}'" # Quote strings<br> elif isinstance(var_value, (list, dict, tuple)):<br> # For collections, convert to their boolean evaluation<br> formatted_value = str(bool(var_value))<br> else:<br> formatted_value = str(var_value)<br> # Replace the variable reference with the formatted value<br> eval_expr = eval_expr.replace(f"${{{var_name}}}", formatted_value)<br> try:<br> return eval(eval_expr) # type: ignore[no-any-return]<br> except Exception as e:<br> raise ValueError(<br> f"Error evaluating expression '{self.expression}' (are you sure you're using ${{my_context_variable_key}}): {str(e)}"<br> )<br>

ContextExpression

``autogen.ContextExpressiondataclass

``expressioninstance-attribute

evaluate

``autogen.ContextExpression`dataclass`

``expression`instance-attribute`

`evaluate`