Can’t escape the backslash in a regular expression?

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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.

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