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

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! π

## What Is An Octal Escape Sequence?π‘

An Octal Escape Sequence is a backslash followed by 1-3 octal digits (`0-7`) such as `\150` which encodes the ASCII character `'h'`. Each octal escape sequence encodes one character (except invalid octal sequence `\000`). You can chain together multiple octal escape sequences to obtain a word.

## Problem Formulation

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

## 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:

```>>> 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 `bytes.decode('unicode-escape')` function converts a given `bytes` object represented by an (octal) escape sequence to a Python string. For example, `br'\101'.decode('unicode-escape')` yields the Unicode (string) character `'A'`.

```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:

```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:

``````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 `c` and convert it to an octal escape sequence using `oct(ord(c))`.

The result uses octal representation such as `'0o123'`. You can do string manipulation, such as slicing and string concatenation, to bring it into the final version `'\123'`, for instance.

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

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

β Background:

• The `ord()` function takes a character (=string of length one) as an input and returns the Unicode number of this character. For example, `ord('a')` returns the Unicode number `97`. The inverse function of `ord()` is the `chr()` function, so `chr(ord('a'))` returns the original character `'a'`.
• The `oct()` function takes one integer argument and returns an octal string with prefix `"0o"`.

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

```strings = ['ABC',
'A B C',
'abc',
'hello',
'hello world']

for s in strings:
print(string_to_octal(s))```

And here’s the expected output:

``````\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:

```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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