Last updated on October 1, 2016
Backslash escaping is common in programming. Sometimes we may let a file go through a few filters or template engines, such as markdown, quik, etc. and things become even worse if we are writing the template files from a string which requires backslash escaping for any literal backslashes appearing in the string. On Windows, things are more horrible than on Unices (You know why, right? Hint: path separator). Then, if you need a “real” backslash in the final output, you may end up with four or eight or sixteen backslashes in the original file. This is horrible. To avoid this situation, I wrote a short preprocessing script
backbackslash.py in Python to double or quadruple or octuple or zzzuple your backslashes.
# Often when your file needs to go through a few filters, the number of # backslashes needed for escaping is just horrible! This small script just # solves the problem. Works well on Python 2.6 and later as well as Python 3. # This file is under public domain. # Copyright (C) 2013 Hong Xu <firstname.lastname@example.org> from __future__ import print_function import sys def escape(content, times, escapechar='\\'): """ Escape the @escapechar for @times times. The content is either a string or an iterative of strings. """ es = escapechar for i in range(times): es = es + es if type(content) is str: return content.replace(escapechar, es) else: ret =  for c in content: ret.append(c.replace(escapechar, es)) return ret if __name__ == '__main__': if len(sys.argv) < 2: print("Error: How many times will you escape?", file=sys.stderr) sys.exit(1) times = int(sys.argv) if len(sys.argv) >= 3: escapechar = sys.argv else: escapechar = '\\' content = sys.stdin.readlines() content = escape(content, times, escapechar) for line in content: sys.stdout.write(line)
This file is also available on Github Gist.
I named it “backbackslash.py”, which means to pull back backslashes. This script is pretty simple—whenever the script encountered a backslash (or other escaping character you specify), it copies the number of the backslashes to 2^N, where N is the times of escaping you will do. To use this script, simply copy it somewhere, then run:
python /path/to/backbackslash.py [number of times to escape] [optional escaping character] output.ext
For example, I have a markdown file, but I need it to go through quik first then markdown. In this way, one single literal backslash would need four backslashes in the original file. So:
python /path/to/backbackslash.py 2 my_preprocessed_markdown.md
Then you can use the output file as the input of the template engines and filters.
This file can also used as in a Python script. See the
escape function in the source file above. You’ll find it pretty easy to understand.