How to replace a double backslash with a single backslash in python?

Question

I have a string. In that string are double backslashes. I want to replace the double backslashes with single backslashes, so that unicode char codes can be parsed correctly.

(Pdb) p fetched_page
'<p style="text-align:center;" align="center"><strong><span style="font-family:\'Times New Roman\', serif;font-size:115%;">Chapter 0<\\/span><\\/strong><\\/p>\n<p><span style="font-family:\'Times New Roman\', serif;font-size:115%;">Chapter 0 in \\u201cDreaming in Code\\u201d give a brief description of programming in its early years and how and why programmers are still struggling today...'

Inside of this string, you can see escaped unicode character codes, such as:

\\u201c

I want to turn this into:

\u201c

Attempt 1:

fetched_page.replace('\\\\', '\\')

but this doesn't work -- it searches for quadruple backslashes.

Attempt 2:

fetched_page.replace('\\', '\')

But this results in an end of line error.

Attempt 3:

fetched_page.decode('string_escape')

But this had no effect on the text. All the double backslashes remained as double backslashes.

Answer 1

You can try codecs.escape_decode, this should decode the escape sequences.

Answer 2

I'm not getting the behaviour you describe:

>>> x = "\\\\\\\\"
>>> print x
\\\\
>>> y = x.replace('\\\\', '\\')
>>> print y
\\

When you see '\\\\' in your output, you're seeing twice as many slashes as there are in the string because each on is escaped. The code you wrote should work fine. Trying printing out the actual values, instead of only looking at how the REPL displays them.

Answer 3

To extend on Jeremy's answer, your problem is that '\' is an illegal string because \' escapes the quote mark, so your string never terminates.

Answer 4

It may be slightly overkill, but...

>>> import re
>>> a = '\\u201c\\u3012'
>>> re.sub(r'\\u[0-9a-fA-F]{4}', lambda x:eval('"' + x.group() + '"'), a)
'“〒'

---

So yeah, the simplest solution would ms4py's answer, calling codecs.escape_decode on the string and taking the result (or the first element of the result if escape_decode returns a tuple as it seems to in Python 3). In Python 3 you'd want to use codecs.unicode_escape_decode when working with strings (as opposed to bytes objects), though.

Answer 5

Python3:

>>> b'\\u201c'.decode('unicode_escape')
'“'

or

>>> '\\u201c'.encode().decode('unicode_escape')
'“'

Answer 6

Just print it:

>>> a = '\\u201c'
>>> print a
\u201c