Formatted text in Linux Terminal (using Python)

indianpythonista — Sun, 02 Apr 2017 04:33:38 +0000

Note: This article has also featured on geeksforgeeks.org .

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.

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

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

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!

linux – Indian Pythonista

Formatted text in Linux Terminal (using Python)