Lists: exercises - SOLVED

Exercise

Make a list of the first 7 powers of 3 (\(3^1\), \(3^2\), etc.).

a = []
for i in range(1,8):
  k = 3**i
  a.append(k)

print(a)

[3, 9, 27, 81, 243, 729, 2187]

Exercise

Make a list of the first 100 odd numbers. Check that it’s 100 long.

b = []
ncount = 0
current_number = 1

while ncount < 100:
  if current_number % 2 != 0:
    b.append(current_number)
    ncount += 1
  current_number += 1

print(b)
print(len(b))

[1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179, 181, 183, 185, 187, 189, 191, 193, 195, 197, 199]
100

Important: a for loop doesn’t have to just use range. It can also iterate through a list that you provide. Here’s an example:

for x in [1, 2., 'a']:
    print(x)

1
2.0
a

Exercise: a nested loop

Write a nested for loop (one loop inside another) that prints a truth table for the ‘or’ operator. Use two variables a and b that take all combinations of True and False, and show the value of (a or b). For example, you should have

a b => (a and b)
True True => True
True False => True
False True => True
False False => False

for a in [True,False]:
  for b in [True,False]:
    c = a or b
    print(f"{a} {b} => {c}")

True True => True
True False => True
False True => True
False False => False