Instead of writing a value, we can write the name of a variable and the value will get substituted.

These two different programs have the same result

    print("bob")

    name = "bob"
    print(name)

The first program uses the value directly.

The second program uses a variable.

The variable gets substituted when that instruction is executed.

    name = "bob"
    print(name)
    name = "alice"
    print(name)

In this example, the instruction print(name) is the same, but it has different results.

When the computer is executing instructions, if it finds a variable name, it replaces it with the variables value.

In this example, the important instructions are:

• we see a function call, but this function needs a value to print, not a variable.
• so, we perform substitution and replace the variable name with the value "bob"
• then we call the print function with the value "bob"
• then we change the value of the variable to "alice"
• then when we perform substitution of the name variable, it is replaced with "alice"
• so the second call to print is given the value "alice"

The following code should print the name, but the variable has not been created when the substitution happens. Remember, the code is run in order. Can you fix it?