Question

Is there any way to modify the bound value of one of the variables inside a closure? Look at the example to understand it better.

def foo():     var_a = 2     var_b = 3      def _closure(x):         return var_a + var_b + x      return _closure   localClosure = foo()  # Local closure is now 'return 2 + 3 + x' a = localClosure(1) # 2 + 3 + 1 == 6  # DO SOME MAGIC HERE TO TURN 'var_a' of the closure into 0 # ...but what magic? Is this even possible?  # Local closure is now 'return 0 + 3 + x' b = localClosure(1) # 0 + 3 +1 == 4 

Answer 1

I don’t think there is any way to do that in Python. When the closure is defined, the current state of variables in the enclosing scope is captured and no longer has a directly referenceable name (from outside the closure). If you were to call foo() again, the new closure would have a different set of variables from the enclosing scope.

In your simple example, you might be better off using a class:

class foo:         def __init__(self):                 self.var_a = 2                 self.var_b = 3          def __call__(self, x):                 return self.var_a + self.var_b + x  localClosure = foo()  # Local closure is now 'return 2 + 3 + x' a = localClosure(1) # 2 + 3 + 1 == 6  # DO SOME MAGIC HERE TO TURN 'var_a' of the closure into 0 # ...but what magic? Is this even possible? localClosure.var_a = 0  # Local closure is now 'return 0 + 3 + x' b = localClosure(1) # 0 + 3 +1 == 4 

If you do use this technique I would no longer use the name localClosure because it is no longer actually a closure. However, it works the same as one.