I am trying to implement a way to let users give a limited possibility to
define functions in text, that wille be stored and executed at a later time. I
use exec() to transform the text to a function. The code is as follows:
class code(str):
def __call__(self, *args):
try:
return self._func_(*args)
except AttributeError:
self._func_ = self._creat_func_()
return self._func_(*args)
def __getstate__(self):
return {}
class _lambdacode(code):
def _creat_func_(self):
return eval("lambda %s: %s" % (", ".join(type(self).args), self),{},{})
class _functioncode(code):
def _creat_func_(self):
exec("def function(%s):\n\t%s" % (", ".join(type(self).args),
"\n\t".join(self.split('\n'))))
return function
def lambdatype(*argnames):
return type('lambdacode', (_lambdacode,),{'args': argnames})
def functiontype(*argnames):
return type('functioncode', (_functioncode,),{'args': argnames})
if __name__ == '__main__':
f = lambdatype('a', 'b')('a ** b')
print f
print f(3, 4)
print f(4, 3)
g = functiontype('a', 'b')('a, b = a/b, a*b\nreturn a ** b')
print g
print g(3.0, 4.0)
print g(4.0, 3.0)
This code works. But if I replace _functioncode with:
class _functioncode(code):
def _creat_func_(self):
exec("def function(%s):\n\t%s" % (", ".join(type(self).args),
"\n\t".join(self.split('\n'))),{})
return function
or
class _functioncode(code):
def _creat_func_(self):
exec("def function(%s):\n\t%s" % (", ".join(type(self).args),
"\n\t".join(self.split('\n'))),{},{})
return function
to restrict access to global variables, similar to the lambda version, i get
the error:
Traceback (most recent call last):
File
"D:\Documents\Code\Eclipse\workspace\FlowWare_1\toolshed\tests\mini_test.py",
line 41, in <module>
print g(3.0, 4.0)
File
"D:\Documents\Code\Eclipse\workspace\FlowWare_1\toolshed\tests\mini_test.py",
line 13, in __call__
self._func_ = self._creat_func_()
File
"D:\Documents\Code\Eclipse\workspace\FlowWare_1\toolshed\tests\mini_test.py",
line 25, in _creat_func_
return function
NameError: name 'function' is not defined
which seems an odd error, but i think some global variable is necessary for
this to work (if i put in globals() instead of {}, it works).
My question is which variable or if that is not the problem, what is and how
can i restrict access the user code has.
Cheers, Lars
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