Formatted text in Linux Terminal using Python

This article demonstrates how to print formatted text in Linux terminal using Python programming language.

Formatted text(also called styled text or rich text) as opposed to plain text, has styling information like:

• color (text color, background color),
• style (bold or italic),
• and some other special features like Strike-through text, underlined text, hyperlinks, etc.

In a Linux Terminal, ANSI escape codes (or escape sequences) are used to control the formatting, color, and other output options.

To encode this formatting information, certain sequences of bytes are embedded into the text, which the terminal looks for and interprets as commands and executes them.

Let us go through a basic example of printing formatted text through a simple Python print statement!

print('\x1b[3;31;43m' + 'Hello world!' + '\x1b[0m')

If you run this code on Linux Terminal, you will obtain an output like this:

As you can see, the output has:

• text-color(foreground color): Red
• background color: Yellow
• text-style: Italic

Now, let us try to understand the meaning of the ANSI escape codes used in above print statement.

• First ANSI escape code used is:

  \x1b[3;31;43m
  

  The general syntax of this code is:

  \x1b[A;B;C
  

  Here,

  • A: text formatting style. It can take any value from 1 to 9.
    

    Value	Style
    1	bold
    2	faint
    3	italic
    4	underline
    5	blinking
    6	fast blinking
    7	reverse
    8	hide
    9	strikethrough

  • B: text color or foreground color. It can take any value form 30-37.
  • C: background color. It can take any value form 40-47.
    

    B(for text)	C(for background)	Color
    30	40	black
    31	41	red
    32	42	green
    33	43	yellow
    34	44	blue
    35	45	magenta
    36	46	cyan
    37	47	white

• At the end, we use this ANSI escape code:

  \x1b[0m
  

  This is the code used to reset the color/style changes to default values.

Now, we create a class in Python to achieve required formatting systematically!

# A python class definition for printing formatted text on terminal.
# Initialize TextFormatter object like this:
# >>> cprint = TextFormatter()
#
# Configure formatting style using .cfg method:
# >>> cprint.cfg('r', 'y', 'i')
# Argument 1: foreground(text) color
# Argument 2: background color
# Argument 3: text style
#
# Print formatted text using .out method:
# >>> cprint.out("Hello, world!")
#
# Reset to default settings using .reset method:
# >>> cprint.reset()

class TextFormatter:

    COLORCODE = {
        'k': 0,  # black
        'r': 1,  # red
        'g': 2,  # green
        'y': 3,  # yellow
        'b': 4,  # blue
        'm': 5,  # magenta
        'c': 6,  # cyan
        'w': 7   # white
    }

    FORMATCODE = {
        'b': 1,  # bold
        'f': 2,  # faint
        'i': 3,  # italic
        'u': 4,  # underline
        'x': 5,  # blinking
        'y': 6,  # fast blinking
        'r': 7,  # reverse
        'h': 8,  # hide
        's': 9,  # strikethrough
    }

    # constructor
    def __init__(self):
        self.reset()

    # function to reset properties
    def reset(self):
        # properties as dictionary
        self.prop = { 'st': None, 'fg': None, 'bg': None }
        return self

    # function to configure properties
    def cfg(self, fg, bg=None, st=None):
        # reset and set all properties
        return self.reset().st(st).fg(fg).bg(bg)

    # set text style
    def st(self, st):
        if st in self.FORMATCODE.keys():
            self.prop['st'] = self.FORMATCODE[st]
        return self

    # set foreground color
    def fg(self, fg):
        if fg in self.COLORCODE.keys():
            self.prop['fg'] = 30 + self.COLORCODE[fg]
        return self

    # set background color
    def bg(self,bg):
        if bg in self.COLORCODE.keys():
            self.prop['bg'] = 40 + self.COLORCODE[bg]
        return self

    # formatting function
    def format(self, string):
        w = [self.prop['st'],self.prop['fg'], self.prop['bg']]
        w = [ str(x) for x in w if x is not None ]
        # return formatted string
        return '\x1b[%sm%s\x1b[0m' % (';'.join(w), string) if w else string

    # output formatted string
    def out(self, string):
        print(self.format(string))

This is the class definition of our text formatter.

In order to use it, save above Python script as TextFormatter.py and open terminal in the same folder where this file is stored.

Then, run Python interpreter through the terminal and import TextFormatter.

Given below is a screen-shot of a sample run:

Here,

• We import TextFormatter class from TextFormatter module using:

  from TextFormatter import TextFormatter

• Then, create an object of TextFormatter class using:

  cprint = TextFormatter()

• Configure formatting of text using cprint.cfg method. Here, argument 1 is text-color, argument 2 is background color and argument 3 is text style.

  cprint.cfg('y', 'g', 'b')

• Now, simply print any statement using cprint.out method like this:

  cprint.out("Hello, world!")

So, now, you can print styled text on terminal with ease!

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