What I like about the appended module is it exercises constructs in a somewhat meaningless fashion that nevertheless has a story, a strong metaphor. We're in a spooky castle and want to leave having guessed a Python keyword, hidden in self.__xyjk during initialization.
If we guess it right in five tries, an exception is raised, but one signalling we're victorious, and so the __exit__ method handles it in a congratulatory manner and returns True, and we're released from the castle without fuss or bother. If we can't guess it in five tries, even after two hints, then the exception is a kick in the pants; we're booted out with an unhandled exception (return False). The outer handler takes care of KickFromCastle in that case. The print() statements tell the story. All pretty pointless... except to those learning Python. Tonight I interleaved the code below with a more serious-looking use of context managers in a Jupyter Notebook. http://bit.ly/2aiFaIA <--- looks through nbviewer (Jupyter Notebook viewer) at one of my Github JNs (just another web page) Kirby == from keyword import kwlist from random import choice import sys class EscapeVictorious(Exception): pass class KickFromCastle(Exception): pass class Castle: def __init__(self, secret): self.__xyjk = secret self.guesses = 0 self.hints = 0 def __enter__(self): """get the ball rolling""" print("Welcome to Spooky Castle. To Escape, " "guess the secret keyword") return self # <-- make me available within scope via 'as' def hint(self): if self.hints == 0: print("The keyword begins with", self.__xyjk[0]) elif self.hints == 1: print("The keyword is", len(self.__xyjk), "letters long.") else: print("You've had your two hints, sorry") self.hints += 1 def query(self): """gradations""" print("So what is the secret keyword then? " " Guess so far:", self.guesses) ans = input("You may answer (or type 'hint'): ") if ans == self.__xyjk: print("Excellent, we're done here") print("You have won the Copper Key") # <-- RealPlayer One (novel) raise EscapeVictorious("Copper Key") elif self.guesses == 5: print("Uh oh, you're out of guesses, sigh") raise KickFromCastle("We're done!") elif ans == "hint": self.hint() return else: self.guesses += 1 print("No, that's not it.") def __exit__(self, *exception_data): """raise a ruckus""" if exception_data[0] == EscapeVictorious: print("Congratulations!") print("Here is your", exception_data[1]) return True if exception_data[0] == KickFromCastle: print("Better Luck Next Time") print("The keyword was", self.__xyjk) return False if __name__ == "__main__": the_secret = choice(kwlist) try: with Castle(the_secret) as spooky: while True: spooky.query() except: print("Handling: ", sys.exc_info()[0].__name__) print(sys.exc_info()[1]) # <--- triggers __str__ print(type(sys.exc_info()[1]))
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