In computing, a regular expression, also referred to as regex or regexp, provides a concise and flexible means for matching strings of text, such as particular characters, words, or patterns of characters.
The following examples illustrate a few specifications that could be expressed in a regular expression:
- The sequence of characters "car" appearing consecutively in any context, such as in "car", "cartoon", or "bicarbonate"
- The sequence of characters "car" occurring in that order with other characters between them, such as in "Icelander" or "chandler"
- The word "car" when it appears as an isolated word
- The word "car" when preceded by the word "blue" or "red"
- The word "car" when not preceded by the word "motor"
- A dollar sign immediately followed by one or more digits, and then optionally a period and exactly two more digits (for example, "$100" or "$245.99").
Python regular expression syntax follows in the Perl lineage. The Python module re provides regular expression functionality. Regular Expressions are a sub-language embedded within the larger Python language.
Please post regex excercises and questions below. We can help each other learn and explore this robust and slightly difficult aspect of Python.