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Python Regular Expressions in Python Introduction to Regular Expressions Word Length

Sandu Gabriel
Sandu Gabriel
2,563 Points

I can't manage to figure out how to stop the findall at the right times

I cant resolve this problem, I tried in different ways, also with sets .

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)

1 Answer

Steven Parker
Steven Parker
221,070 Points

You've got the right idea, but you don't want the word "count" in your regex. To get the value represented by the variable "count" instead, you could use concatenation to put the string version of the value into the regex:

    return re.findall(r'\w{' + str(count) + ',}', string)

Another way would be to use a formatted string to insert the value using interpolation:

    return re.findall(f'\w{{{count},}}', string)
nakalkucing
nakalkucing
12,964 Points

Hi Steven Parker! I couldn't quite figure out this challenge and I ended up using your code to pass. But I still don't understand the code. Would you mind telling me why you used the plus signs and what the "f" is for in your second bit of code? :) Thanks.

Steven Parker
Steven Parker
221,070 Points

When used with a string, a plus sign is a concatenation operator. This is just the method of joining strings together to make a longer one.

The "f" in the second example indicates a formatted string. This causes string interpolation where an expression enclosed in curly braces will be replaced by its value.

Both methods put the value of the count into the regex instead of the word "count" itself.