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| import sys
import ast
blacklist = [ast.Call, ast.Attribute]
def check(node):
if isinstance(node, list):
return all([check(n) for n in node])
else:
"""
expr = BoolOp(boolop op, expr* values)
| BinOp(expr left, operator op, expr right)
| UnaryOp(unaryop op, expr operand)
| Lambda(arguments args, expr body)
| IfExp(expr test, expr body, expr orelse)
| Dict(expr* keys, expr* values)
| Set(expr* elts)
| ListComp(expr elt, comprehension* generators)
| SetComp(expr elt, comprehension* generators)
| DictComp(expr key, expr value, comprehension* generators)
| GeneratorExp(expr elt, comprehension* generators)
-- the grammar constrains where yield expressions can occur
| Yield(expr? value)
-- need sequences for compare to distinguish between
-- x < 4 < 3 and (x < 4) < 3
| Compare(expr left, cmpop* ops, expr* comparators)
| Call(expr func, expr* args, keyword* keywords,
expr? starargs, expr? kwargs)
| Repr(expr value)
| Num(object n) -- a number as a PyObject.
| Str(string s) -- need to specify raw, unicode, etc?
-- other literals? bools?
-- the following expression can appear in assignment context
| Attribute(expr value, identifier attr, expr_context ctx)
| Subscript(expr value, slice slice, expr_context ctx)
| Name(identifier id, expr_context ctx)
| List(expr* elts, expr_context ctx)
| Tuple(expr* elts, expr_context ctx)
-- col_offset is the byte offset in the utf8 string the parser uses
attributes (int lineno, int col_offset)
"""
attributes = {
'BoolOp': ['values'],
'BinOp': ['left', 'right'],
'UnaryOp': ['operand'],
'Lambda': ['body'],
'IfExp': ['test', 'body', 'orelse'],
'Dict': ['keys', 'values'],
'Set': ['elts'],
'ListComp': ['elt'],
'SetComp': ['elt'],
'DictComp': ['key', 'value'],
'GeneratorExp': ['elt'],
'Yield': ['value'],
'Compare': ['left', 'comparators'],
'Call': False,
'Repr': ['value'],
'Num': True,
'Str': True,
'Attribute': False,
'Subscript': ['value'],
'Name': True,
'List': ['elts'],
'Tuple': ['elts'],
'Expr': ['value'],
}
for k, v in attributes.items():
if hasattr(ast, k) and isinstance(node, getattr(ast, k)):
if isinstance(v, bool):
return v
return all([check(getattr(node, attr)) for attr in v])
if __name__ == '__main__':
expr = sys.stdin.readline()
body = ast.parse(expr).body
if check(body):
sys.stdout.write(repr(eval(expr)))
else:
sys.stdout.write("Invalid input")
sys.stdout.flush()
|