[Tut] How to Convert an Octal Escape Sequence in Python – And Vice Versa?

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How to Convert an Octal Escape Sequence in Python – And Vice Versa?

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This tutorial will show you how to convert an

• octal escape sequence to a Python string, and a
  
  
• Python string to an octal escape sequence.
  

But let’s quickly recap what an octal escape sequence is in the first place!

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What Is An Octal Escape Sequence?

An Octal Escape Sequence is a backslash followed by 1-3 octal digits (

Code:

0-7

) such as

Code:

\150

which encodes the ASCII character

Code:

'h'

. Each octal escape sequence encodes one character (except invalid octal sequence

Code:

\000

). You can chain together multiple octal escape sequences to obtain a word.

Problem Formulation

Question: How to convert an octal escape sequence to a string and vice versa in Python?

Examples

Octal |
String

Code:

\101 \102 \103

|

Code:

'ABC'

Code:

\101 \040 \102 \040 \103

|

Code:

'A B C'

Code:

\141 \142 \143

|

Code:

'abc'

Code:

\150 \145 \154 \154 \157

|

Code:

'hello'

Code:

\150 \145 \154 \154 \157 \040 \167 \157 \162 \154 \144

|

Code:

'hello world'

Python Octal to String Built-In Conversion

You don’t need to “convert” an octal escape sequence to a Unicode string if you already have it represented by a bytes object. Python automatically resolves the encoding.

See here:

Code:

>>> b'\101\102\103' b'ABC' >>> b'101\040\102\040\103' b'101 B C' >>> b'\101\040\102\040\103' b'A B C' >>> b'\141\142\143' b'abc' >>> b'\150\145\154\154\157' b'hello' >>> b'\150\145\154\154\157\040\167\157\162\154\144' b'hello world'

Python Octal to String Explicit Conversion

The

Code:

bytes.decode('unicode-escape')

function converts a given

Code:

bytes

object represented by an (octal) escape sequence to a Python string. For example,

Code:

br'\101'.decode('unicode-escape')

yields the Unicode (string) character

Code:

'A'

.

Code:

def octal_to_string(x): ''' Converts an octal escape sequence to a string''' return x.decode('unicode-escape')

Example: Convert the octal representations presented above:

Code:

octals = [br'\101\102\103', br'\101\040\102\040\103', br'\141\142\143', br'\150\145\154\154\157', br'\150\145\154\154\157\040\167\157\162\154\144'] for octal in octals: print(octal_to_string(octal))

This leads to the following expected output:

Code:

ABC A B C abc hello hello world

Python String to Octal

To convert a Python string to an octal escape sequence representation, iterate over each character

Code:

c

and convert it to an octal escape sequence using

Code:

oct(ord(c))

.

The result uses octal representation such as

Code:

'0o123'

. You can do string manipulation, such as slicing and string concatenation, to bring it into the final version

Code:

'\123'

, for instance.

Here’s the function that converts string to octal escape sequence format:

Code:

def string_to_octal(x): ''' Converts a string to an octal escape sequence''' return '\\' + '\\'.join(oct(ord(c))[2:] for c in x)

Background:

• The
  Code:

  ord()
  function takes a character (=string of length one) as an input and returns the Unicode number of this character. For example,
  Code:

  ord('a')
  returns the Unicode number
  Code:

  97
  . The inverse function of
  Code:

  ord()
  is the
  Code:

  chr()
  function, so
  Code:

  chr(ord('a'))
  returns the original character
  Code:

  'a'
  .
  
  
• The
  Code:

  oct()
  function takes one integer argument and returns an octal string with prefix
  Code:

  "0o"
  .
  

Let’s check how our strings can be converted to the octal escape sequence representation using this function:

Code:

strings = ['ABC', 'A B C', 'abc', 'hello', 'hello world'] for s in strings: print(string_to_octal(s))

And here’s the expected output:

Code:

\101\102\103 \101\40\102\40\103 \141\142\143 \150\145\154\154\157 \150\145\154\154\157\40\167\157\162\154\144

If you don’t like the one-liner solution provided above, feel free to use this multi-liner instead that may be easier to read:

Code:

def string_to_octal(x): ''' Converts a string to an octal escape sequence''' result = '' for c in x: result += '\\' + oct(ord(c))[2:] return result

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