The conversation between human and AI assistant.
[|Human|] Explain why the following code won't execute properly.
[|AI|] The code won't execute properly because `bar` is not defined. In order for the code to work, `bar` must first be defined as a function, class or variable before being called or invoked. 

Without any prior definition or import, Python would raise an exception that says `NameError: name 'bar' is not defined`.
[|Human|] 
Explain why the following code won't execute properly.