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Intermediate Python Programming LAB 6 Page: 2 o This method accepts a name string and will assign it to self.name def str_(self): This method will output a string in the following format: "{self.name}" O Teller The Teller class represents a teller that will help customers in the bank. This class will have only two methods: _init__() and __str_0 def __init__(self, name): This method accepts a name string and will assign it to self.name def str_(self): This method will output a string in the following format: "{self.name}" o . o bankprint The bankprint() function will be where all print commands are sent. It has the following signature: def bankprint(lock, msg): . Where: lock is a Lock object that must be acquired before the print() function is called. Hint: Use a with context manager block on the lock object msg is the text to print. . Main Block This block will use the standard check for name__ and represents the entry point for the program: if name == "_main__": In this block, create the printlock Lock object which will be passed to all of the thread functions and used by bankprint(): printlock = Lock() Next, create a Queue called teller_line which represents the line customers get into waiting for a teller (the maxsize parameter need to be set to the max_customers_in_bank value): teller_line = Queue (maxsize=max_customers_in_bank) Now, you need a Semaphore object that represents a security guard. A semaphore only allows a limited number of threads to acquire a resource at the same time, just as a security guard limits the number of customers allowed in the bank at once. Like the queue, this object will also be limited to max_customers_in_bank semaphore resources:
Intermediate Python Programming LAB 6 Page: 3 guard = Semaphore (max_customers_in_bank) Finally after the guard is created, print several messages to the terminal by using the bankprint() method: bankprint (printlock, "<G> Security guard starting their shift") bankprint (printlock, "*B* Bank open") Notice that the printlock argument is passed to bankprint(). Also, each message is preceded with a tag of sorts. This will help distinguish output in what will be a very busy terminal/shell. For this code, use the following prefixes: *B* for bank messages <G> for security guard messages [T] for teller messages (C) for customer messages You will be adding more code to the main section after that last bankprint() statement in following parts. Scoring: Criteria Teller class Customer class bankprint() function Main block TOTAL Points 5 5 5 10 25 Part II - Get Customers into the Bank Now, in the __main_ section, you are going to create the Customer objects that want to go into the bank. This can be done several different ways, such as using a for loop or a comprehension. The key requirements are: You must create max_customers Customer objects Each Customer object must have a unique name remember, that is the only argument to Customer's _init__() function) Now, each customer must be passed to a thread function, wait_outside_bank(), which we have to define now. We will get back to __main__ in a moment... def wait_outside_bank(customer, guard, teller_line, printlock):
Intermediate Python Programming LAB 6 Page: 4 Where: customer is a Customer object guard is the security guard semaphore teller_line is the Queue printlock is the Lock The thread function must do the following: Print a customer message indicating that the customer is waiting outside the bank Attempt to acquire a semaphore from the guard object (do NOT use a context manager here since the semaphore is to be released in another method) Print a security guard message indicating they have let that customer into the bank Print a customer message indicating they are trying to get into line Put the customer into the teller_line queue (queue's put() method) Back in the _main_section, after the customer objects are created, spawn a Thread object for each one using the following criteria: . target = wait_outside_bank args = (customer, guard, teller_line, printlock) • Now, start each of those threads (you can do it in the same loop as the Thread creation). Finally, sleep for 5 seconds to give time for the tellers to get to work. Points 5 5 Scoring: Criteria Customer object creation wait_outside_bank() Proper output and use of bankprint() Acquire semaphore from security guard Put customer into the teller_line queue Thread spawning TOTAL num 5 5 10 35 Part III - Get the Tellers to Service the Customers Now, you need to create a thread method, teller_job(), that will allow customers to be served by tellers: def teller_job (teller, guard, teller_line, printlock):
Intermediate Python Programming LAB 6 Page: 5 . Where: teller is a Teller object guard is the security guard semaphore teller_line is the Queue printlock is the Lock As you can see, the parameters are almost the same as wait_outside_bank(). The major difference is the first one which is now a teller since, unlike the other thread which was customer-centric, this one will be teller-centric. o . Print a teller message indicating that this teller has started work Create an infinite loop and put the rest of the code in it Use a try block, and place the following code within it (see the except code later): Get a customer from the teller_line (use queue's get method() - provide teller_timeout for the timeout argument) Print a teller message indicating this teller is now helping this customer Sleep a random amount of time (1 - 4 seconds) to simulate the teller working with the customer Print a teller message indicating this teller is done helping this customer Print a security guard message indicating they are letting this customer out of the bank Release the semaphore from the guard object The except block should handle a Queue.Empty error (just Empty is OK due to the import) Print a teller message indicating that the teller is going on break and exit the loop o Back in __main__ it is time to get the tellers to work. So, immediately after the 5 second sleep completed in Part II, do the following: Print a bank message indicating the tellers are going to start working now Create a list of Teller objects (the number should be max_tellers) Create a list of teller threads that target the teller_job method using the following arguments to the Thread initializer method: target = teller_job args (one of the teller objects, guard, teller_line, printlock) Launch all the teller threads Wait for all threads to complete Print a bank message indicating the bank is closed and let the program end o Points 5 Scoring: Criteria teller_job Proper output and use of bankprint() Proper retrieval of customer from teller line Release of semaphore 5 5 5