File: safeeval.py

package info (click to toggle)
lilypond 2.19.81+really-2.18.2-13
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 68,528 kB
  • sloc: cpp: 76,619; ansic: 75,407; lisp: 56,140; xml: 31,046; python: 20,799; sh: 7,946; yacc: 3,266; perl: 3,045; asm: 1,587; lex: 1,405; makefile: 1,048; tcl: 457; awk: 199; php: 53; csh: 50
file content (84 lines) | stat: -rw-r--r-- 2,439 bytes parent folder | download | duplicates (8)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84

## http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/364469
import compiler

class Unsafe_Source_Error(Exception):
    def __init__(self,error,descr = None,node = None):
        self.error = error
        self.descr = descr
        self.node = node
        self.lineno = getattr(node,"lineno",None)
        
    def __repr__(self):
        return "Line %d.  %s: %s" % (self.lineno, self.error, self.descr)
    __str__ = __repr__    
           
class SafeEval(object):
    
    def visit(self, node,**kw):
        cls = node.__class__
        meth = getattr(self,'visit'+cls.__name__,self.default)
        return meth(node, **kw)
            
    def default(self, node, **kw):
        for child in node.getChildNodes():
            return self.visit(child, **kw)
            
    visitExpression = default
    
    def visitConst(self, node, **kw):
        return node.value

    def visitDict(self,node,**kw):
        return dict([(self.visit(k),self.visit(v)) for k,v in node.items])
        
    def visitTuple(self,node, **kw):
        return tuple(self.visit(i) for i in node.nodes)
        
    def visitList(self,node, **kw):
        return [self.visit(i) for i in node.nodes]

    def visitUnarySub(self, node, **kw):
        return - self.visit (node.getChildNodes ()[0])

class SafeEvalWithErrors(SafeEval):

    def default(self, node, **kw):
        raise Unsafe_Source_Error("Unsupported source construct",
                                node.__class__,node)
            
    def visitName(self,node, **kw):
        raise Unsafe_Source_Error("Strings must be quoted", 
                                 node.name, node)
                                 
    # Add more specific errors if desired
            

def safe_eval(source, fail_on_error = True):
    walker = fail_on_error and SafeEvalWithErrors() or SafeEval()
    try:
        ast = compiler.parse(source,"eval")
    except SyntaxError, err:
        raise
    try:
        return walker.visit(ast)
    except Unsafe_Source_Error, err:
        raise


def safe_eval(source, fail_on_error = True):
    walker = fail_on_error and SafeEvalWithErrors() or SafeEval()
    try:
        ast = compiler.parse(source,"eval")
    except SyntaxError, err:
        raise
    try:
        return walker.visit(ast)
    except Unsafe_Source_Error, err:
        raise

def test ():
    print safe_eval ('{1: [2,3], "4": (-1,2)}')
    
if __name__ == '__main__':
    test ()