def sub_expr(expr: ast.Expr, env: List[Dict[str, str]]) -> ast.Expr:
if type(expr) == ast.Name:
return ast.Str(env[expr.id])
elif type(expr) == ast.Compare:
expr = copy.deepcopy(expr)
expr.left = sub_expr(expr.left, env)
expr.comparators = [sub_expr(x, env) for x in expr.comparators]
return expr
elif type(expr) == ast.Str:
return expr
elif type(expr) == ast.Subscript:
if type(expr.value) == ast.Name:
if type(expr.slice) == ast.Index:
return ast.Str(env[expr.value.id][expr.slice.value.n])
elif type(expr.slice) == ast.Slice:
return ast.Str(
env[expr.value.id][expr.slice.lower.n:expr.slice.upper.n])
raise Exception(ast.dump(expr))
