Programming Across Disciplines

Home » Chapter 2 : Programming Basics
Printing

Overview
Common Use & Examples
Printing in Python
Print Function General Form
Practice Problems

Overview

The first step we will take to learn programming and Python is printing to the screen. We often think "printing" means to print on paper, but in our context, for now, we will print text, numbers and symbols on the computer screen. Printing on the screen is a simple form of output and allows us to quickly see the results of our programming efforts. Printing on the screen in this form is not graphical, that is, the screen will only display textual output (letters, numbers, and symbols). For now, this is sufficient to give us a way to learn the basics of Python programming. Later, after you have mastered the basics, you can explore Graphical User Interface (GUI) programming where you will be able to interact with graphics programmatically as well. Recognized by its name followed by parentheses, the print() function is built into Python, meaning that you can use it without any preparations or installations. Inside the parentheses, you place the information you wish to display, known as arguments, enclosed in quotes if you're dealing with text (e.g., print("Hello, World!")). The print() function is not limited to one type of data—it is versatile, allowing numbers, variables, and even complex expressions to be included as arguments. As you progress, you will find that the print() function is an invaluable tool in Python.

Concept: Input - Processing - Output

In computing we frequently use the terms input, processing, and output. Input is anything that is entered into the computer, such as characters typed on a keyboard, mouse clicks, taps on the screen, recording our voice, recording video, information from sensors, and many others. Processing is what happens to those inputs inside the computer, including calculations, storing values in memory or on hard drives, uploading input data to the Internet, etc. And output is the result of processing, including displaying results on the screen, printing on paper, playing video or sounds, etc.

In Python we use the print() function to print alphanumeric characters (the alphabet, numeric digits, and other symbols) on the computer screen. The print() function is versitile and has a number of different ways we can use it.

Concept: Strings

In Python we call text strings. Strings are characters, words, or phrases and contain from one to any number of valid alphanumeric symbols surrounded by quotes (" "). Alphanumeric symbols include the letters of the alphabet, numeric digits (when included in a string, numbers are not numeric but characters of the string), all of the other symbols on the keyboard (~!@#$%^&*()_+=-`{}|[]\:";'<>?,./'`), and extended characters from non-English languages, etc.

Printing Text (Strings)

Try the following examples of printing strings in your editor:

Python Code:

print("Hello, World!")
print("Hello,", "World!")
print("Hello" + "," + " " + "World" + "!")
print("Hello", "World", sep=", ", end="!")

If you wrote these examples exactly the same in your environment and ran them, the output should look like this:

Output:

Hello, World!
Hello, World!
Hello, World!
Hello, World!

Code & Output Details:

First note that all four variations of the print() statement in this example prints the same output.
Code Lines 1 thru 4: Study the difference in syntax between these four lines.
Code Line 1: This is a single string Hello, World! inside the quotes (" ") so the print() function prints the contents of the quotes directly.
Code Line 2: This line demonstrates two separate strings, Hello, and World! each inside their own set of quotes (" "). The print() function concatenates the two strings together to print them as one line of output. Pay close attention to the fact that there is no space after the comma in the first string and no space preceding the W in the second string. How does the space get in the output then? Be default, in Python, if you place separate strings in a print() function and separate them with a comma, the print() function will add one blank space between those two strings. Sometimes this is exactly what you need (like in this example), but sometimes you need more control over the precise output. In those cases, you might use the techniques shown in Code Lines 3 or 4.
Code Line 3: This line demonstates another, more precise, approach to concatenation. In this case, rather than rely on the print() function to place an automatic blank space between individual strings (each enclosed in quoted (" ")), we can use the plus (+) operator to indicate how we want the strings concatenated. In this example, each piece of our overall string is separated into component parts and concatenated together using the plus operator.
Code Line 4: This line demonstrates yet another approach using the print() function's sep and end arguments (see the General Form section below) to specify how to separate the two strings in the concatenated output, and what symbol we want at the end of the concatenated output.

String concatenation is a valuable technique that allows you to combine or join multiple strings. This operation is beneficial when creating longer or more complex strings. Python offers different ways to perform string concatenation. One of the simplest methods is using a comma (,) between strings. For example, if you have two strings, "Hello" and "world", you can concatenate them in a print statement like this:

Python Code:

print("Hello", "world")

Output

Hello world

Concept: Concatenation

Concatenation refers to the act of combining or linking things together in a sequence or series. In the context of programming or computer science, concatenation often specifically refers to joining strings together to create a single, long string. This is accomplished by placing one string after another, effectively merging their characters or contents. String concatenation is a commonly used when working with text or manipulating data in programming languages.

Another method of concatenation is using the plus (+) operator. For example, if you have those same two strings, "Hello" and "world", you can concatenate them using the expression "Hello" + "world", like this:

Python Code:

print("Hello" + "world")

Output

Helloworld

Notice the problem we have, though; using the + operator our two strings have no space between them, which is because the + operator does exactly what we tell it to do. In this case, we said put these two strings (words) together. Without any other instructions, we get exactly what we asked for.

What if what we wanted was this:

Python Code:

Hello, world!

The word Hello is followed by a comma and a space and then the word world followed by an exclamantion point? We have several options to do this. Here is the code for several approaches and then an explanation of each:

print("Hello" + ", world!")
print("Hello" + ", " + "world" + "!")
print("Hello", end=", ")
print("world!")
print("Hello", end=", ")
print("world", end="!")
print("Hello", "world", sep=", ", end="!")

Output

Hello, world!
Hello, world!
Hello, world!
Hello, world!
Hello, world!

Code & Output Details

Code Line 1: This line includes the comma, space, and exclamation point inside the quotes of the second string, which works, it gives us the output we want (Output Line 1), but we'll see later (when we talk about variables) that including punctuation inside of a string might not be possible.
Code Line 2: This line uses separate string objects for the ", " and the "!", which is a better approach than Line 1 because it keeps the strings separate, and we could use other strings in place of Hello and world, and this would work well.
Code Lines 3 & 4: These lines work together to create the correct output. This approach uses the end argument of the print() function (see the table above) to have the function add ", " to the end of the string "Hello" and then the ! is included in the string "world!". This is a good use of the end argument, however, we'll see a little later (when we talk about variables) that including punctuation inside of a string might not be possible.
Code Lines 5 & 6: These lines work together to create the correct output. This approach uses the end argument of the print() function (see the table above) to have the function add ", " to the end of the string "Hello" and the end argument to add the ! to the world string, which is a better approach as it keeps the original strings and the punctuation separate.
Code Line 7: This line combines the use of the sep and end arguments of the print function to create our desired output all in one line, which is the best approach.

Next, try the following examples of printing numbers in your editor:

Python Code:

print(10)
print(10, 20, 30)
print(10 + 20 + 30)

If you wrote these examples exactly the same in your environment and ran them, the output should look like this:

Output:

10
10, 20, 30
60

Code & Output Details:

Code Line 1: When printing a literal numeric value we do not use quotes (" "). If you enclose a number in quotes, Python will interpret it as a string.
Code Line 2: We can also print more than one number in one print() function statement by separating them by commas.
Code Line 3: This line demonstrates that we can also perform calculations inside of the print() function. The result of the calculation is the output printed to the screen.

We can also combined printing strings and numbers together in a single print() function statement. The following examples demonstrate how we might combine strings and numbers in print() function statements.

Python Code:

print("Age:", 21)
print("Age: " + str(21))
print("Sum: " + str(10 + 20 + 30))

If you wrote these examples exactly the same in your environment and ran them, the output should look like this:

Output:

Age: 21
Age: 21
Sum: 60

Code & Output Details:

Code Line 1: This line demonstrates using the print() function to print a string and a number. In this case, the two values are separated by a comma, which as we saw previously, automatically adds a space between the two objects. In addition, the comma in this case also separates the fact that the two objects of differt types of data (a string and an integer). The print() functioncan print them in this form to look like they are together even though they are actually separate in the code.
Code Line 2: On this line, we want to concatenate the label Age with the integer value to make one single string. In this case, we must use the casting function str() to convert the number value to a string so that it can be concatenated with the label Age.
Code Line 3: As we saw previously, we can perform calculations in print() function statements. In this case, because we are also tring to concatenate the resulting numeric calculated value with the label Sum, we need to use casting here as well.

Concept: Casting

In programming, we often need to convert data from one type to another type. For example, in Code Lines 2 & 3 of this Python code ...

print("Age: " + str(21))
print("Sum: " + str(10 + 20 + 30))

... requires us to cast (convert) the numeric values to strings so that we can concatenate those values with our string labels Age and Sum. We do this, in this case, using the str() function, which casts numeric values to string values. The process of converting (casting) data from one type to another is called casting.

Argument	Description
object(s)	Any objects in Python and any number of objects. Objects that are not a string of alphanumeric characters are converted to alphanumeric equivalents for printing. Here is an example of a print function call with two objects as arguments. For example: `print("Hi", "Bob")` The output of this print function call would be Hi Bob. Notice the space between "Hi" and "Bob". The reason for this is explained in the sep=separator argument described below.
sep=separator	Optional argument. When you specify more than one object to print in one argument list, you can also specify how those objects are separated when printed. The default is a blank space " ". You could change this to any other one or more characters by indicating it here in the second argument of the function call. For example: `print("Hey", "What's up?", sep=", ")` This print function statement has two object arguments: "Hey" and "What's Up?", and the sep=", " indicates that when this statement runs, it should print Hey, What's up? Notice that the sep=", " includes a comma and a space after it so that when the two objects print, they will be formatted properly with a space between the comma and the next word.
end=end	Optional argument. You can use this argument to append (add) one or more characters to the end of the output. For example: `print("Hi", "Bob", end="!")` This print function statement has two object arguments, "Hi" and "Bob", and it includes end="!" which results in the output: Hi Bob!. We did not have the sep argument this time, so we got the single default space " " as the separator between the two objects.
file=file	Optional argument. This argument is used with objects a bit more complex than simple alphanumeric strings of characters. We will revisit this argument later in the book.
flush=flush	Optional argument. This argument is used to manipulate how data is handled internally, which is a bit more complex of a concept for now. We will revisit this argument later in the book.

Read the following programming prompts and write a program that solves the problem in your programming environment. Do not read the Solution until you try to solve it yourself first. Once you have completed writing your code, run your program, click the Solution button and compare your work.

Note: There is often more than one way to write solutions in programming. Your solution may not match the solution provided below exactly, which is generally fine if you're getting the required results. Use the provided solution as an example of an approach to learn from while not interpreting it as the only "right" solution.

Problem 1

Write a Python program using the print() function to output the following contact information. Your output should match the format and lines shown here:

Bob Smith
1234 Nowhere Street
Someplace, UT 84999
(801)555-8888
bob@smithco.com

print("Bob Smith")
  print("1234 Nowhere Street")
  print("Someplace, UT 84999")
  print("(801)555-8888")
  print("bob@smithco.com")

Solution Notes:

The function name print is lower-case.
We use a print statement for each new line of the output. Later we will learn other ways to do this.
Each line of text that we want to print to the screen is enclosed inside of quotes, including the special characters ( ) , and -.

Problem 2

Write a Python program using the print() function with two object arguments and also use the sep and end arguments to print the following output:

Wow, that's great news!

print("Wow", "that's great news", sep=", ", end="!")

Solution Notes:

The function name print is lower-case.
We have two objects: "Wow" and "that's great news".
The sep argument will place a comma and a space between the two objects in the output.
the end argument will add the ! to the end of the sentence.

Problem 3

Write a Python program using the print() function with three object arguments to construct a (fictitious) social security number. The three object arguments should be the three sets of numbers that make up an SSN, like 123-45-6789. Also, use the sep argument to separate the three sets of numbers with a dash symbol. Here is an example of the output:

111-22-3333

print("111", "22", "3333", sep="-")

Solution Notes:

The function name print is lower-case.
We have three objects: "111", "22" and "333".
The sep argument will place a dash between each of the three objects in the output.
Note that if we specify more than one object and a sep argument, the sep will appear between each object no matter how many objects there are in the list.

Overview

Concept: Input - Processing - Output

Study Tip

Menu

Common Use & Examples

Printing in Python

Concept: Strings

Printing Text (Strings)

Python Code:

Output:

Study Tip

Concatenation

Python Code:

Output

Concept: Concatenation

Python Code:

Output

Python Code:

Output

Code & Output Details

Printing Numbers

Python Code:

Output:

Code & Output Details:

Printing Strings & Numbers Together

Python Code:

Output:

Code & Output Details:

Concept: Casting

Print Function General Form

Concept: Arguments

Practice Problems

Problem 1

Problem 2

Problem 3