- Validate that strings match specific patterns using regular expressions.
- Search for strings that match specific patterns using regular expressions.
- Regular Expression: a sequence of characters used to search for a pattern inside of a string.
- Pattern: a description of sequences of characters that share certain traits with one another. Sequences do not need to be the same length or share any common characters to pattern match. Also called a filter.
This is a test-driven lab. Run pipenv install to create your virtual
environment and pipenv shell to enter the virtual environment. Then run
pytest -x to run your tests. Use these instructions and pytest's error
messages to complete your work in regex.py in the lib folder.
This lab is meant to give you experience with writing patterns for regular
expressions and using the re module to check your pattern against different
strings. Use regex101 to test your pattern as you work through the
different strings.
- Run
pytest -xto execute the first test. This will check your RegEx against the string"It's such a lovely day today." - Once you've compiled a regular expression that matches this first string,
run
pytest -xagain to check against the next string in line. - Your RegEx should match all of the strings in the test file!
- The last test uses the
findall()method to search for these three strings in a list. You can check for this list intesting/regex_test.py.- If you hacked your way through the first three with
r".*", you'll get caught here!
- If you hacked your way through the first three with
Once all of your tests are passing, commit and push your work using git to
submit.
Regular expressions can be confusing and frustrating. You'll only get used to them with practice. That being said, there are some tools and tricks that will help you our along the way:
\wis shorthand for any word character:[A-Za-z0-9_].\Wis shorthand for anything outside of that range.- Similarly to
\w,\Swill match any non-whitespace character- though it includes characters not found in words as well.\smatches any single whitespace character. - Getting quotes, backslashes, and other operational characters into your regex
requires that you lead with an escape character, the backslash (
\). - Ignoring a specific set of characters (say, 'c', 'h', 'a', 'r', 's') can be
accomplished with square brackets and carrots (
^): [^chars]. - Matching one pattern or another with the same regex can be accomplished with
the
|operator:r'hello|goodbye'. - regex101 provides a "Quick Reference" section in the bottom right corner that is very helpful for more tips and tricks along the way.