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"""This module defines parsing utility methods.
"""
import ast
[docs]class ExprVarScanner(ast.NodeVisitor):
"""
This node visitor collects all variable names found in the
AST, and excludes names of functions. Variables having
dotted names are not supported.
"""
def __init__(self):
self.varnames = set()
# noinspection PyPep8Naming
[docs] def visit_Name(self, node):
self.varnames.add(node.id)
# noinspection PyPep8Naming
[docs] def visit_Call(self, node):
if not isinstance(node.func, ast.Name):
self.visit(node.func)
for arg in node.args:
self.visit(arg)
# noinspection PyPep8Naming
[docs] def visit_Attribute(self, node):
# ignore attributes
pass
[docs]def get_variables(expr):
"""Parses the given Python expression and return a list of all variables.
Parameters
----------
expr : str
An expression string that we want to parse for variable names.
Returns
-------
var_list : list[str]
Names of variables from the given expression.
"""
root = ast.parse(expr, mode='exec')
scanner = ExprVarScanner()
scanner.visit(root)
return list(scanner.varnames)