Callbacks and functions as values in Python

Questions 1 to 5 of 7

1. 1. Match each built-in function to what it does with the function you pass in.

   Choose the matching item for each row.

   filter(f, items)Choose…orders the items by the value `f` gives for each onegives the item whose value from `f` is the largestgives `f(item)` for each itemkeeps the items for which `f(item)` is truemap(f, items)Choose…orders the items by the value `f` gives for each onegives the item whose value from `f` is the largestgives `f(item)` for each itemkeeps the items for which `f(item)` is truesorted(items, key=f)Choose…orders the items by the value `f` gives for each onegives the item whose value from `f` is the largestgives `f(item)` for each itemkeeps the items for which `f(item)` is truemax(items, key=f)Choose…orders the items by the value `f` gives for each onegives the item whose value from `f` is the largestgives `f(item)` for each itemkeeps the items for which `f(item)` is true
2. 2. What does this program print? (one value per line) ``python def double_it(n): return n * 2 def add_one(n): return n + 1 def compose(f, g): return lambda x: g(f(x)) print(compose(double_it, add_one)(5)) print(compose(add_one, double_it)(5)) ``

   10, then 1112, then 1111, then 1211, then 11
3. 3. What does this program print? ``python offset = 10 shifted = lambda a, b: a + b + offset offset = 20 print(shifted(1, 2)) ``

   13, because the lambda keeps the value 10 it saw when it was madeAn error, because a lambda cannot read a variable that changes23, because the lambda reads offset when it runs3, because offset is reset to zero before the lambda runs
4. 4. Match each situation to the type hint that fits it. The hints come from the typing module, and T and R stand for any types.

   Choose the matching item for each row.

   Takes no input, gives back nothingChoose…`Callable[[], T]``Callable[[T], bool]``Callable[[T], R]``Callable[[], None]`Takes no input, gives back a valueChoose…`Callable[[], T]``Callable[[T], bool]``Callable[[T], R]``Callable[[], None]`Takes one input, gives back True or FalseChoose…`Callable[[], T]``Callable[[T], bool]``Callable[[T], R]``Callable[[], None]`Takes one input, gives back a new valueChoose…`Callable[[], T]``Callable[[T], bool]``Callable[[T], R]``Callable[[], None]`
5. 5. What is the last line this program prints? ``python class Button: def __init__(self, name): self.name = name self.handlers = [] def on_click(self, handler): self.handlers.append(handler) def click(self): print(self.name, "clicked") for handler in self.handlers: handler() save_count = 0 def count_save(): global save_count save_count += 1 print("save count is", save_count) save = Button("Save") save.on_click(lambda: print("writing file")) save.on_click(count_save) save.click() save.click() print("total", save_count) ``

   save count is 2total 2total 0Save clicked