Embercode: AI-powered software engineer course

1. What happens when this code runs? ``

python
values = [4, 0, 9]
i = 3
if values[i] != 0 and i < len(values):
    print('ok')

``

It prints ok, because and skips the second test when the first is False.It prints nothing, because the check fails safely.It stops with IndexError: list index out of range, because the read runs before the length check.It does not run, because and must come before the list read.

2. This code is supposed to print "in range" only for a valid index, but it crashes on the last line. Why does the check say "in range" for index 5? ``

python
values = [4, 0, 9]
index = 5
if index >= 0 or index < len(values):
    print('in range')
print(values[index])

``

Because or is True when either side is True, and 5 >= 0 is already True, so the check passes. It should use and with both tests.Because index 5 is less than len(values), which is 3.Because >= cannot compare a list index with 0.Because the check runs after the read on the last line.

3. What does this program print? ``

python
calls = 0

def check(r):
    global calls
    calls += 1
    return r

a = check(True) and check(False) and check(True)
b = check(False) or check(True) or check(True)
print(a, b, calls)

``

False True 2False True 4True True 4False False 3

4. What does this program print? ``

python
v = [7, 9, 4]
i = 2
j = 2
v[i] = v[i] ^ v[j]
v[j] = v[j] ^ v[i]
v[i] = v[i] ^ v[j]
print(v)

``

[7, 9, 4][0, 9, 4][7, 9, 0][7, 0, 4]

5. Write the Python keyword that joins the two tests index >= 0 and index < len(values) in a guard, so that the list read after the guard runs only when both tests are true. Give the keyword.

Type your answer.

Guards and XOR in Python