There is nothing named x

Something in your program, or something you typed at the prompt, refers to a variable name which is not defined.

• Did you spell the variable name correctly? (Remember that capitalization matters!)
• Did you forget to import a module which defines the variable you want?
• Are you trying to refer to a variable outside of the context in which it is defined? For example, a parameter to a function can only be used inside the function itself.
• Did you forget to put double quotes around a string, for example, hello instead of "hello"?

If you got this error due to something else not on the list above, please add it as a suggestion!