Python Programming

The *, +, ?, and {M,N} quantifiers apply only to the single previous character. So hello* only repeats the o.

To repeat groups of characters, use parenthesis to group the characters together. For example, (baa)+ matches baa, baabaa, baabaabaa, etc.

Quick task

Write a regular expression that matches the string:

• starts with "oh" (one or more times)
• followed by "yeah" (zero or more times)
• it can end optionally with the word "baby" (at most once)

So the following strings are valid: "oh", "oh oh", "oh oh yeah yeah yeah", "oh yeah yeah baby", "oh baby", "oh oh baby", and "oh oh yeah yeah yeah baby".

Beware of how you include your spaces between the words!

👀 Peek at sample solutions

>>> pattern = "(oh)( oh)*( yeah)*( baby)?" 
>>> re.match(pattern, "oh")
<re.Match object; span=(0, 1), match='oh'>
>>> re.match(pattern, "oh oh yeah yeah yeah")
<re.Match object; span=(0, 20), match='oh oh yeah yeah yeah'>
>>> re.match(pattern, "oh baby")
<re.Match object; span=(0, 7), match='oh baby'>
>>> re.match(pattern, "baby baby yeah") # None