Basic Types & None

You want to check whether a result is the "no value" sentinel. Why prefer if x is None: over if x == None:?

What is the type of None, and how many instances of it exist at runtime?

What does this print? ``` def greet(name): print("hi", name) result = greet("Sam") print(result) ```

What does this print? ``` nums = [3, 1, 2] result = nums.sort() print(result) ```

Is `None` truthy or falsy, and what does this print? ``` x = None if x: print("yes") else: print("no") ```

In Python, every value is an object with a type. What is the idea behind type(x), and what does type(5) return?

What does this print, and why does `+` behave differently on each line? ``` print(1 + 2) print("1" + "2") ```

Python operators fall into a few categories. Name the category each of these belongs to: +, <, and, is, in.

What does this print? ``` print(2 * 3 + 4) print(2 * (3 + 4)) ```

What does this print, and what general rule decides it? ``` print(10 - 4 - 3) ```

What does the chained comparison 1 < 2 < 3 evaluate to, and how does Python expand it?

Which operators support chaining like `a < b <= c`, and what does this print? ``` x = 5 print(1 < x == 5) ```

What does this print, and why isn't the result a plain `True`/`False`? ``` print(0 or "hello") print("a" and "b") ```

What is the difference between is and in, given x = [1, 2, 3]?

Which binds tighter — a comparison like `==` or a logical `and`? What does this print? ``` print(True == False and False) ```

What does this print, and which precedence gotcha causes it? ``` print(not 1 == 1) ```

Of Python's built-in types, which are mutable? Sort these: list, tuple, dict, set, frozenset, str, bytes, bytearray, int.

Are an empty dict {}, an empty set set(), and an empty frozenset() truthy or falsy?

What does this print, and why? a = True if a or print("Lazy"): print("Evaluation")

A user is prompted for their age. What does this print, or does it fail? age = input("Age: ") # user types 30 print(age + 1)