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My stab at safe python evaluation

View expressify.py
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import ast
import math
 
SAFE_FX = {
'exp': math.exp,
}
 
SAFE_NODES = set(
(ast.Expression,
ast.Num,
ast.Call,
ast.Name,
ast.Load,
ast.BinOp,
ast.Add,
ast.Sub,
ast.Mult,
ast.Div,)
)
 
class CleansingNodeVisitor(ast.NodeVisitor):
def generic_visit(self, node):
if type(node) not in SAFE_NODES:
raise Exception("%s not in SAFE_NODES" % type(node))
super(CleansingNodeVisitor, self).generic_visit(node)
 
def visit_Call(self, call):
if call.func.id not in SAFE_FX:
raise Exception("Unknown function: %s" % call.func.id)
 
def safe_eval(s):
tree = ast.parse(s, mode='eval')
cnv = CleansingNodeVisitor()
cnv.visit(tree)
compiled = compile(tree, s, "eval")
return(eval(compiled, SAFE_FX))
 

why not add a few more functions, like math.log, math.sin, &c., or maybe some numpy functions? this is super similar to JF Sebastians ast parser

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