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Python Regular Expressions in Python Introduction to Regular Expressions Word Length

Y B
Y B
14,136 Points
Posted by Y B
Y B
14,136 Points

findall challenge doesn't quite work

Using the code below fails the test, however if I replace count by 4 in the example then the code seems to work fine. I'm not clear why using the variable count in place of the 4 stops it being recognised and produces the empty list?

word_length.py 
import re

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

def find_words(count, string):
  return re.findall(r'\w{count}', string)

3 Answers

Michael De Marre
Michael De Marre
14,198 Points

Using count inside of the string prevents Python from detecting it as a variable. Try multiplying the escape character string by count and then adding it to zero or more escape characters. Your answer should have two different strings.

Y B
Y B
14,136 Points
Y B
Y B
14,136 Points

That makes sense but I couldn't get that to work either...

def find_words(count, string):
  return re.findall(r'\w'*count, string)

ps what is the escape character?

Kenneth Love
Kenneth Love
Treehouse Guest Teacher
Kenneth Love
Kenneth Love
Treehouse Guest Teacher

The escape character is \. You want count+ occurrences, though, so you need to get the count into the string. If only there was some way to concatenate strings together... :D

Kenneth Love
STAFF
Kenneth Love
Treehouse Guest Teacher
Kenneth Love
Kenneth Love
Treehouse Guest Teacher

How is the count variable getting into your pattern?

Y B
Y B
14,136 Points
Y B
Y B
14,136 Points

I did question that at one point I tried using the format method as per the earlier course on string so I tried

def find_words(count, string):
    return re.findall(r'\w{}'.format(count), string)

but that just gave me the empty list? Format doesn't feel like the right method here, although perhaps it's effectively putting the int count into the {} to get e.g. '\w{4}' which worked for the example. So I'm not sure why this doesn't work?

Y B
Y B
14,136 Points
Y B
Y B
14,136 Points

4+ or count+, I hadn't grasped that I needed the + at all. Thanks for your very patient help.