print_foobar.py

Suppose you are given the following code:

class FooBar {
  public void foo() {
    for (int i = 0; i < n; i++) {
      print("foo");
    }
  }

  public void bar() {
    for (int i = 0; i < n; i++) {
      print("bar");
    }
  }
}
The same instance of FooBar will be passed to two different threads. Thread A will call foo() while thread B will call bar(). Modify the given program to output "foobar" n times.

# -----------------------------------------------------------------------------------------------------
Use two locks for the threads to signal to each other when the other should run. bar_lock starts in a locked state because we always want foo to print first.

import threading

class FooBar:
    def __init__(self, n):
        self.n = n
        self.foo_lock = threading.Lock()
        self.bar_lock = threading.Lock()
        self.bar_lock.acquire()

    def foo(self, printFoo):
        for i in range(self.n):
            self.foo_lock.acquire()
            printFoo()
            self.bar_lock.release()

	def bar(self, printBar):
        for i in range(self.n):
            self.bar_lock.acquire()
            printBar()
            self.foo_lock.release()