Can't escape the backslash with regex?

Question

I\'m using the following regex

^[a-zA-Z0-9\\\',!;\\?\\$\\^:\\\\\\/`\\|~&\\\" @#%\\*\\{}\\(\\)_\\+\\.\\s=-]{1,1000}$

I know it\'s ugly,

Answer 1

If you're putting this in a string within a program, you may actually need to use four backslashes (because the string parser will remove two of them when "de-escaping" it for the string, and then the regex needs two for an escaped regex backslash).

For instance:

regex("\\\\")

is interpreted as...

regex("\\" [escaped backslash] followed by "\\" [escaped backslash])

is interpreted as...

regex(\\)

is interpreted as a regex that matches a single backslash.

---

Depending on the language, you might be able to use a different form of quoting that doesn't parse escape sequences to avoid having to use as many - for instance, in Python:

re.compile(r'\\')

The r in front of the quotes makes it a raw string which doesn't parse backslash escapes.