What Are ANSI Escape Codes?#

ANSI escape sequences were introduced in the 1970s as a standard to style text terminals with color, font styling, and other options. They are supported by most modern terminals in operating systems like Windows, macOS, and Linux.

Building Blocks#

Escape Character#

They always start with \x1b, \033, \u001b, or \e or depending on the operating system or programming language. Technically this inserts byte 27 into a string, which is equivalent to 0x1b and the ESC key when you look at an ASCII table. Hence the name.

Escape Character	Description
`\x1b`	Hexadecimal
`\033`	Octal
`\u001b`	Unicode
`\e`	Escape in C
`27`	Decimal

This first part is called the Control Sequence Introducer (CSI), whichever option you use. For convenience, we will use \x1b as the escape character throughout this section.

Sequence Parts#

All ANSI escape sequences follow the same pattern. For example, the sequence \x1b[31m can be broken down into:

Part	`\x1b[`	`31`	`m`
Description	Starts sequence, also called the Control Sequence Introducer (CSI).	Color code for various text and background colors, e.g. between `30`-`49` or `90`-`109`.	Ends sequence and calls the graphics function Select Graphic Rendition (SGR).

Examples#

Though ANSI escape sequences appear in a string as multiple characters, they are in reality interpreted by the terminal as a single command. For example:

Sequence	Description
`\x1b[31m`	Change the color to red
`\x1b[0m`	Reset any styling

Imagine that we want to achieve the following terminal output:

% I want RED color

We simply wrap the word RED with the ANSI escape sequences \x1b[31m to set the color and \x1b[0m to reset the color. The terminal will then interpret this as a single command while the characters of the escape sequences are hidden in the terminal output. The user only sees the changed color.

How to apply this in a print command:

Python

print("I want \x1b[31mRED\x1b[0m color")

You can use the same method to apply other colors to text or backgrounds.

Humanised Sequence Is Easier to Read

This is also why it's convenient to use Colorist instead of manually writing raw ANSI escape codes.

The Color class will generate the ANSI escape sequences and keep the code readable. For example:

Python
from colorist import Color

print(f"I want {Color.RED}RED{Color.OFF} color")

The result in the terminal output is the same as before:

% I want RED color