Escaping characters in python just once (single backlash)

Question

I want to escape a string from this:

str1 = "this is a string (with parentheses)"

to this:

str2 = "this is a string \(with parentheses\)"

That is, a single \ escape character at the parentheses. This is to be fed to another client which needs to escape these characters and will only work with a single escaping slash.

For simplicity I focus below on the opening parentheses only, i.e. changing from '(' to '\(' So far I tried:

1. replace

   str1.replace("(", "\(")
   'this is a string \\(with parentheses)'
   

2. sub

   re.sub( "\(", "\(", str1)
   'this is a string \\(with parentheses)'
   

3. Escape dictionary with raw string

   escape_dict = { '(':r'\('}
   "".join([escape_dict.get(char,char) for char in str1])
   'this is a string \\(with parentheses)'
   

Whatever the case I always get double backlash. Is there a way to get only one?

Answer 1

You are confusing the string representation with the string value. The double backslash is there to make the string round-trippable; you can paste the value back into Python again.

The actual string itself has just one backslash.

Take a look at:

>>> '\\'
'\\'
>>> len('\\')
1
>>> print '\\'
\
>>> '\('
'\\('
>>> len('\(')
2
>>> print '\('
\(

Python escapes the backslash in string literal representations to prevent it from being interpreted as an escape code.