What is "raw strings"?

What's this?

• I'm rereading the Python tutorial for review.
• I'll try to organize the definition and role of "raw strings".

What I learned.

Escape sequences

The particular expressions started from (backslash) are recognized as particular meanings in string.

docs.python.org

For example, \t means Tab, and \n means LF.

s = 'a\tb\nA\tB'
print(s) # => a       b
         #    A       B

In Python, we can use both single and double quotations to express string, but we cannot usually use single quotations in a single quotation.

Then, by using an escape sequence, we can use single quotations in a single quotation.
(Of course, we can also use a double quotation.)

# s = 'a'b' => SyntaxError: unterminated string literal
s = 'a\'b'
print(s) # => a'b

Raw strings

Definition

String literals may optionally be prefixed with a letter 'r' or 'R'.
Such strings are called "raw strings".

They treat backslashes as literal characters.

r = r'a\tb\nA\tB'
print(r) # => a\tb\nA\tB

Details

Technically, there is no "raw string type", but string literals that can be prefixed with a letter 'r' or 'R'.

print(type(r)) # => <class 'str'>

python - What exactly do "u" and "r" string prefixes do, and what are raw string literals? - Stack Overflow

As defined, raw strings manipulate backslashes as just backslashes, so we can see the difference when converting them into lists.

print(list(s)) # => ['a', "'", 'b']
print(list(r)) # => ['a', '\\', 't', 'b', '\\', 'n', 'A', '\\', 't', 'B']

When we can use it

We can utilize it when manipulating regular expressions.

For instance, we should use \\\\ to match the string \ because String \\ is interpreted as \ and \\ in regular expressions is interpreted as \.

re — Regular expression operations — Python 3.11.7 documentation

import re

text = '\\begin'
print(re.search('\\begin', text)) # => None
print(re.search('\\\\begin', text)) # => <re.Match object; span=(0, 6), match='\\begin'>

On the contrary, when using raw strings, we can implement it more simply.

text = r'\begin'
print(re.search(r'\\begin', text)) # => <re.Match object; span=(0, 6), match='\\begin'>

Impression on Implementation

• I almost got into the swamp of regular expressions...
• I found it difficult that things used casually are manipulated correctly.