Making decisions

The last missing piece in our basic set of commands is the ability to make decisions in a program. This is done in Python using the if command.

Exercise 1

Execute the following program and explain its output.

number = 123

if number > 1000:
    print("The number is larger than 1000.")
elif number == 1000:
    print("The numer is exactly 1000.")
else:
    print("The number is smaller than 1000.")

Exercise 2

Set name to such a value that one, two or all three conditions apply.

name = ____

if "m" in name:
    print("There is a 'm' in the name.")
    if name != "Mimi":
        print("The name is not Mimi.")
        if name[0] == "M" and name[-1] == "m":
            print("The name starts and ends with m.")

Exercise 3

The following program writes the positions of all letters "n" in the name to the screen. Unfortunately, it contains three errors. Make the program execute correctly:

name = "Anna"
position = 1

for char in name
    if char = "n":
        print(position)
position = position + 1

Exercise 4

Which of these if statements are syntactically correct?

• if a and b:
• if len(s) == 23:
• if a but not b < 3:
• if a ** 2 >= 49:
• if a != 3
• if (a and b) or (c and d):