There are several cases where Python statements are illegal when used in conjunction with nested scopes that contain free variables.
If a variable is referenced in an enclosing scope, it is illegal to delete the name. An error will be reported at compile time.
If the wild card form of import -- "import *" -- is used in a function and the function contains or is a nested block with free variables, the compiler will raise a SyntaxError.
If exec is used in a function and the function contains or is a nested block with free variables, the compiler will raise a SyntaxError unless the exec explicitly specifies the local namespace for the exec. (In other words, "exec obj"would be illegal, but "exec obj in ns" would be legal.)
The eval(), execfile(), and input() functions and the exec statement do not have access to the full environment for resolving names. Names may be resolved in the local and global namespaces of the caller. Free variables are not resolved in the nearest enclosing namespace, but in the global namespace.4.1The exec statement and the eval() and execfile() functions have optional arguments to override the global and local namespace. If only one namespace is specified, it is used for both.