13.1. Using Decisions with Strings¶
We can use conditional statements in code to produce different strings for different situations and to treat different strings in different ways. As a first example, here is a program that prints a different message depending on how many item(s) a person orders. Try this program a few times and enter different values for the input.
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In the program, notice that we have to use the int function to turn the input from a string
into an integer. Anytime we use input to get some input from the user, it will be read as
a string. If the user types 20, that will be stored by Python as the string "20" and not
as the numeric value 20. Any time we get input, if we want to work with it as a number and not
as a string (a piece of text that may have digits in it) we will need to use this trick.
Similarly, when we go to construct the string that is the elif response, we are trying to combine
the string "You ordered " with numItems a number. As we have seen before, to make this
work, we need to call the str function to make a string out of the number that can be added
to the other strings.
- It runs the same
- Try it!
- It sometimes produces the wrong answer because it is comparing a string to a number
- Try it!
- There is an error because we are comparing a string to a number
- Correct. You are not allowed to compare a string to a number. Even if the string is something like "2" that looks like a number.
What will happen if you change the first line to remove the int function by making it
numItems = input("How many items do you want?")?