Exercises
Last updated on 2023-05-03 | Edit this page
Overview
Questions
- How do you find and match strings with regular expressions?
Objectives
- Test knowledge of use of regular expressions
Exercises
The exercises are designed to embed the regex knowledge you learned during this module. We recommend you work through it sometime after class (within a week or so).
This matches France, French, in addition to
the misspellings Frence, and Franch. It would
also find strings where there were characters to either side of the
pattern such as France's, in French, or
French-fried.
This matches France, French,
Frence, and Franch only at the end of
a line. It would also match strings with other characters appearing
before the pattern, such as in French or
Sino-French.
^France|^French This would also find strings with other
characters coming after French, such as
Frenchness or France's economy.
In real life, you should only come across the case
insensitive variations colour, color,
Colour, Color, COLOUR, and
COLOR (rather than, say, coLour. So one option
would be \b[Cc]olou?r\b|\bCOLOU?R\b. This can, however, get
quickly quite complex. An option we’ve not discussed is to take
advantage of the / delimiters and add an ignore case flag:
so /colou?r/i will match all case insensitive variants of
colour and color.
\bhead ?rest\b. Note that although
\bhead\s?rest\b does work, it would also match zero or one
tabs or newline characters between head and
rest. In most real world cases it should, however, be
fine.
0+[a-z]{4}\b
\d{4}. Note this will match 4 digit strings only but
will find them within longer strings of numbers.
\b\d{2}-\d{2}-\d{4}\b In most real world situations, you
are likely to want word bounding here (but it may depend on your
data).
\d{2}-\d{2}-\d{2,4}$
.* : .*, \d{4} You will find that this matches any text
you put before British or Manchester. In this
case, this regular expression does a good job on the first look up and
may be need to be refined on a second depending on your real world
application.