Replacing double backslash and brackets in Python

Question

I am trying to write a script that could convert things like \\[ or \\] to $$ in order to convert a MultiMarkdown document to Pandoc markdown document that could display equations in HTML. I am using Python to find all instances of these characters using

 matchstring=r'\\['
 re.sub(matchstring,'$$',content)

However I run into the following error:

unexpected end of regular expression:line 15:matchstring=re.compile(r'\\[')
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.py", line 190:
return _compile(pattern, flags)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.py", line 245:
raise error, v # invalid expression

most likely because of the last [ I have in there. Does anyone know a way to get around this?

score 1 · Answer 1 · answered Mar 21 '13 at 17:55

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Escape the [:

matchstring=re.compile(r'//\[')

Or better yet, use:

content.replace("//[", "$$")

and don't involve regex at all.

answered Mar 21 '13 at 17:55

Mark

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How would I go about multiple replace in the document? I have different patterns to match. Shoudl I be doing `content.replace("//[", "$$")` `content.replace("//]", "$$")` for all the patterns I want to match or is there a better way to do it? – Shruti Kapoor Mar 21 '13 at 18:53
Just realised that I could use `content.replace("//[", "$$")).replace(r"\\]", "$$")` to do multiple iterations of replace. Thanks @Igor! – Shruti Kapoor Mar 21 '13 at 23:26

score 1 · Accepted Answer · answered Mar 22 '13 at 04:51

1

pandoc -f markdown_mmd -t markdown

will do this for you! (For pandoc >= 1.11)

answered Mar 22 '13 at 04:51

John MacFarlane

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Oh Wow! thats great to know. – Shruti Kapoor Mar 22 '13 at 17:54

score 0 · Answer 3 · answered Mar 21 '13 at 17:54

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Your problem is that you write r'//[', not r'\\[', but anyway try better this:

matchstring.replace(r'\\[', '$$').replace(r'\\]', '$$')

answered Mar 21 '13 at 17:54

Igor Chubin

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My bad. I mixed up forward and backslashes. Fixed them in the question – Shruti Kapoor Mar 21 '13 at 18:01

score 0 · Answer 4 · answered Mar 21 '13 at 18:26

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if you are using a "[" within your regex, I would assume it would be required to have an escape for it as it is used within regular expression.

try one of the following:

content = "testing123//]testing456"
matchstring = "//]"
result = content.replace(matchstring, "$$")
print result

or

content = "testing123//]testing456"
matchstring = '(//\])'
result = re.sub(matchstring,'$$',content)
print result

Either should work for your purpose.

answered Mar 21 '13 at 18:26

AWainb

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just saw the next comment.. if it is just the "]" characters that are to be replaced, then try: matchstring = "\]" – AWainb Mar 21 '13 at 18:27
the above comment was for the first example. For the second, use matchstring = '(\\])' – AWainb Mar 21 '13 at 18:39
To deal with both at the same time ("[" & "]"), try using something like this: re.sub('(\\]|\\[)','$$',content) – AWainb Mar 21 '13 at 18:43

Replacing double backslash and brackets in Python

4 Answers4