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Python Regular Expressions in Python Introduction to Regular Expressions Word Length

Not Sure..Regex

Not sure what's wrong here, can anyone offer a hand?

word_length.py
import re

# EXAMPLE:
# >>> find_words(4, "dog, cat, baby, balloon, me")
# ['baby', 'balloon']

def find_words(acount, mstr):
  return re.findall(r"\w{acount,},", mstr)

2 Answers

You can use/interpolate variables inside quoted strings, but you'll run into issues trying to use str.format and its curly braces inside the regex curly braces.

One other option besides Adiv Abramson's solution is to use the old string interpolation syntax:

def find_words(acount, mstr):
  return re.findall(r"\w{%s,}" % acount, mstr)

Note that you shouldn't have the trailing comma at the end of your regular expression string because you want to be able to match the last word in the quoted string if necessary.

I believe the problem with your regex, re.findall(r"\w{acount,},", mstr) is that Python doesn't substitute the value of the acount variable where the variable name appears in the regex. I would try something like this:

return re.findall(r'\w{' + str(acount) + ',}',mstr)

Unlike Perl, Python doesn't interpolate variables embedded in a quoted string.