Do regular expressions from the re module support word boundaries (\b)?

python regex word-boundaries
D.C. picture D.C. · Oct 22, 2010 · Viewed 57k times · Source

While trying to learn a little more about regular expressions, a tutorial suggested that you can use the \b to match a word boundary. However, the following snippet in the Python interpreter does not work as expected:

>>> x = 'one two three'
>>> y = re.search("\btwo\b", x)

It should have been a match object if anything was matched, but it is None.

Is the \b expression not supported in Python or am I using it wrong?

Answer

Bolo picture Bolo · Oct 22, 2010

This will work: re.search(r"\btwo\b", x)

When you write "\b" in Python, it is a single character: "\x08". Either escape the backslash like this:

"\\b"

or write a raw string like this:

r"\b"

Related questions

How to extract numbers from a string in Python?

I would extract all the numbers contained in a string. Which is the better suited for the purpose, regular expressions or the isdigit() method? Example: line = "hello 12 hi 89" Result: [12, 89]

Read More
Python string.replace regular expression

I have a parameter file of the form: parameter-name parameter-value Where the parameters may be in any order but there is only one parameter per line. I want to replace one parameter's parameter-value with a new value. I am using …

Read More
Split string on whitespace in Python

I'm looking for the Python equivalent of String str = "many fancy word \nhello \thi"; String whiteSpaceRegex = "\\s"; String[] words = str.split(whiteSpaceRegex); ["many", "fancy", "word", "hello", "hi"]

Read More