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Python Regular Expressions in Python Introduction to Regular Expressions Word Length

Chuang Poching
Chuang Poching
112 Points

word_length.py

I don't know how to write this task. Could anyone tell me why below code is incorrect? Thank you.

word_length.py
import re

# EXAMPLE:
# >>> find_words(4, "dog, cat, baby, balloon, me")
# ['baby', 'balloon']
def find_words(count, s):
    return re.findall(r'\w{,count}',s)

2 Answers

Steven Parker
Steven Parker
229,645 Points

You have the right general idea, but you don't want the word "count" as part of your regex string. Instead, use any method (like concatenation, format function, f-string, token substitution.) to put the value of the count into the string.

Also, to get "count or longer" you need to put the count value in front of the comma.

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,423 Points

You are on the right path. The string "count" in the current regex is literally the characters "count". For the argument count to be evaluated with in the string, it must be inserted into the string. Some methods:

# raw concatenation
r'\w{,' + str(count) + '}'
# f string uses double {{ to escape regular {
fr'\w{{,{count}}}' 
# format uses double {{ to escape regular {
r'\w{{,{}}}'.format(count),s) 
r'\w{{,{count}}}'.format(count=count),s)
# % s
r'\w{,%s}' % count