This material was prepared for the workshop held on 2022-04-07 at the Gymnasium Thun (Thun, Switzerland), and updated for the workshop held on 2022-09-02 at EPFL (Lausanne, Switzerland).

Regex 101

pattern	meaning	usage	matches	doesn't match
\b	word boundary (beginning or end of a word)	apfel\b	apfel in apfel or erdapfel	apfel in apfelsaft
\w	alphanumeric character (= any letter or a digit)	\wier	vier, Bier, hier, Tier	Klavier
[abc]	set (any of the character between brackets)	[vTB]ier	vier, Bier, Tier	hier, Klavier
(abc|def)	group (any of the groups of tokens separated by |)	(Klav|T)ier	Klavier, Tier	Bier
[a]*	0 or more occurrences	[\w]*ier	Klavier, Tier, vier, Bier, Stier, ier
[a]+	1 or more occurrences	[\w]+ier	Klavier, Tier, vier, Bier, Stier	ier
[a]?	0 or 1 occurrences	[s]?tier	tier, stier	vier
^	beginning of a line	^Tiere	Tiere in beginning of a line ("Tiere sind Lebensformen")	Tiere in the middle or end of a line ("So viele Tiere!")

Set Up

1. Open the RegExr webpage https://regexr.com/ in your browser.
2. Set the RegEx engine to "JavaScript (Browser)".
3. Set the Tools to "List".
4. Set the Flags to "global" and "multiline".
5. Open scraped_wiki_neuron.md and copy-paste its contents into the text box of the RegExr website.

Exercises

Try to write regular expressions that extract the following contents from the text.

1. Extract exact mention of the word "neuron". [34 matches]
2. What about uppercase, e.g. at the beginning of a sentence? Extract mention of the word "neuron" or "Neuron". [35 matches]
3. What about plurals? Try to extract "neurons", "Neurons", "neuron", or "Neuron". [105 matches]
4. Now, any word containing "neur" or "Neur" inside of it (e.g. "interneuronal"). [147 matches]
5. Certain words use the root "nerv" to express similar concepts (e.g. "nervous system"). Extract all words containing "neur", "Neur", "nerv", or "Nerv", inside of it. [170 matches]
6. Under the section "Classification" we find a bulleted list of neuron types. They are all in format "Xxxx cells", where "Xxxxx" is an adjective starting with a capital letter like "Basket cells" or "Granule cells". Try to extract all of them. [8 matches]
7. Under the section "Neurotransmitters" we find another bulleted list of neuron types. They are all in format "Xxxx neurons", where "Xxxxx" is an adjective starting with a capital letter like "Cholinergic neurons" or "Purinergic neurons". Try to extract all of them. [9 matches]

Solutions

Click here!

1. \bneuron\b
2. \b[nN]euron\b
3. \b[nN]euron[s]?\b
4. \b[\w]*[nN]eur[\w]*\b
5. \b[\w]*[nN]e(ur|rv)[\w]*\b
6. ^\w+ cells\b
7. ^\w+ neurons\b