When you write an expression in the Python shell, and you run it, the result of the expression is shown below it. For instance, if you type the following command in the shell and press Enter, you see the result \(12\).

5 + 7

However, as I showed in Exercise [python.shell]¹, a program that contains the statement 5 + 7 will not produce a result in the shell. Instead, you have to explicitly display everything that you want to see, even if it is on the last line of the program.

So, even though this chapter is about expressions, the first thing I need to explain is not an expression, but a function, that allows you to display results. The function that does that is print. I already showed the print function in Chapters 2 and 3.

The print function is used as follows: you write the word print, followed by an opening parenthesis, followed by whatever you want to display, followed by a closing parenthesis. For example (and I showed this one before):

print( "Hello, world!" )

If you run this code (by saving it into a Python file and running it in IDLE), you will see that it displays the text “Hello, world!” in the shell.

By the way, when referring to a function by name in a text, authors of texts about programming often put an opening and closing parenthesis after the name of the function, to indicate that it is a function name. From now on, I will follow this convention. Moreover, instead of referring to a “function,” authors sometimes call it a “statement” or a “command.” However, these terms are usually used to refer to anything that Python can execute, not just functions. I.e., an expression can also be called a “command.”

You can display multiple things with one print() function by putting everything that you want to display between the parentheses with commas in between. The print() function will then display all of the items, with one space in between each pair or them. For example:

print( "I", "own", "two", "apples", "and", "one", "banana" )

Note that the spaces in this statement are all superfluous. The statement:

print("I","own","two","apples","and","one","banana")

is equivalent to the previous one. You can add such spaces for readability. You can even put spaces between the word print and the opening parenthesis, but by convention, for functions (and print() is a function), the opening parenthesis is placed against the function name.

Note that you can not only use print() to display texts, but also to display numbers. You can even mix them up, as the following code shows.

print( "I", "own", 2, "apples", "and", 1, "banana" )

Display some texts of your liking using a Python program. But take note that if you want to display text strings, you have to enclose them in double quotes – or single quotes, those work too.