main in Python no longer has a special meaning, but is a regular function, its name only chosen to conform to conventions based in C. Try exit(1) instead of return 1. Relevant python docs: https://docs.python.org/3/library/sys.html#sys.exit


The solution is simple, you are calling the isupper and islower functions without parenthesis, the correct way is: if c.isupper(): if c.islower():


The message is telling you that 'h' cannot be changed to an int. True enough. From the Hints section of the spec: You might find chr and/or ord of help. I think chr is what you want, not int.

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