Watch Now This tutorial has a related video course created by the Real Python team. Watch it together with the written tutorial to deepen your understanding: The Python print() Function: Go Beyond the Basics
If you’re like most Python users, including me, then you probably started your Python journey by learning about print(). It helped you write your very own hello world one-liner. You can use it to display formatted messages onto the screen and perhaps find some bugs. But if you think that’s all there is to know about Python’s print() function, then you’re missing out on a lot!
Keep reading to take full advantage of this seemingly boring and unappreciated little function. This tutorial will get you up to speed with using Python print() effectively. However, prepare for a deep dive as you go through the sections. You may be surprised how much print() has to offer!
By the end of this tutorial, you’ll know how to:
- Avoid common mistakes with Python’s
print() - Deal with newlines, character encodings, and buffering
- Write text to files
- Mock
print()in unit tests - Build advanced user interfaces in the terminal
If you’re a complete beginner, then you’ll benefit most from reading the first part of this tutorial, which illustrates the essentials of printing in Python. Otherwise, feel free to skip that part and jump around as you see fit.
Note: print() was a major addition to Python 3, in which it replaced the old print statement available in Python 2.
There were a number of good reasons for that, as you’ll see shortly. Although this tutorial focuses on Python 3, it does show the old way of printing in Python for reference.
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Printing in a Nutshell
Let’s jump in by looking at a few real-life examples of printing in Python. By the end of this section, you’ll know every possible way of calling print(). Or, in programmer lingo, you’d say you’ll be familiar with the function signature.
Calling print()
The simplest example of using Python print() requires just a few keystrokes:
>>> print()
You don’t pass any arguments, but you still need to put empty parentheses at the end, which tell Python to actually execute the function rather than just refer to it by name.
This will produce an invisible newline character, which in turn will cause a blank line to appear on your screen. You can call print() multiple times like this to add vertical space. It’s just as if you were hitting Enter on your keyboard in a word processor.
A newline character is a special control character used to indicate the end of a line (EOL). It usually doesn’t have a visible representation on the screen, but some text editors can display such non-printable characters with little graphics.
The word “character” is somewhat of a misnomer in this case, because a newline is often more than one character long. For example, the Windows operating system, as well as the HTTP protocol, represent newlines with a pair of characters. Sometimes you need to take those differences into account to design truly portable programs.
To find out what constitutes a newline in your operating system, use Python’s built-in os module.
This will immediately tell you that Windows and DOS represent the newline as a sequence of \r followed by \n:
>>> import os
>>> os.linesep
'\r\n'
On Unix, Linux, and recent versions of macOS, it’s a single \n character:
>>> import os
>>> os.linesep
'\n'
The classic Mac OS X, however, sticks to its own “think different” philosophy by choosing yet another representation:
>>> import os
>>> os.linesep
'\r'
Notice how these characters appear in string literals. They use special syntax with a preceding backslash (\) to denote the start of an escape character sequence. Such sequences allow for representing control characters, which would be otherwise invisible on screen.
Most programming languages come with a predefined set of escape sequences for special characters such as these:
\\: backslash\b: backspace\t: tab\r: carriage return (CR)\n: newline, also known as line feed (LF)
The last two are reminiscent of mechanical typewriters, which required two separate commands to insert a newline. The first command would move the carriage back to the beginning of the current line, while the second one would advance the roll to the next line.
By comparing the corresponding ASCII character codes, you’ll see that putting a backslash in front of a character changes its meaning completely. However, not all characters allow for this–only the special ones.
To compare ASCII character codes, you may want to use the built-in ord() function:
>>> ord('r')
114
>>> ord('\r')
13
Keep in mind that, in order to form a correct escape sequence, there must be no space between the backslash character and a letter!
As you just saw, calling print() without arguments results in a blank line, which is a line comprised solely of the newline character. Don’t confuse this with an empty line, which doesn’t contain any characters at all, not even the newline!
You can use Python’s string literals to visualize these two:
'\n' # Blank line
'' # Empty line
The first one is one character long, whereas the second one has no content.
Note: To remove the newline character from a string in Python, use its .rstrip() method, like this:
>>> 'A line of text.\n'.rstrip()
'A line of text.'
This strips any trailing whitespace from the right edge of the string of characters.
In a more common scenario, you’d want to communicate some message to the end user. There are a few ways to achieve this.
First, you may pass a string literal directly to print():