import re import urllib.request import operator # Download wiki page url = "https://en.wikipedia.org/wiki/Diplomatic_history_of_World_War_II" html = urllib.request.urlopen(url).read() # Find all mentioned years in the 20th or 21st century regex = r"\b(? This is another instance where I would strongly recommend using the well-tested libraries and/or services, along with the use of whitelists instead of blacklists, in order to protect your application from malicious inputs.:19|20)\d\b" matches = re.findall(regex, str(html)) # Form a dict of the number of occurrences of each year year_counts = dict((year, matches.count(year)) for year in set(matches)) # Print the dict sorted in descending order for year in sorted(year_counts, key=year_counts.get, reverse=True): print(year, year_counts[year]) . :[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(? Regex matching speeds can range from not-very-fast to extremely slow, depending on how well the expression is written.In recent versions of Firefox, if a then the field will show a red outline, as illustrated by the following figure. If it did, then every required field would have that outline by default.Instead, these outlines are only shown after you’ve interacted with the field, which is basically (though not precisely) analogous to the instant, as it could easily be triggered on and off many types in rapid succession while typing, creating a flashing effect which would be annoying or impossibly distracting for some users.And, in any case, , and frankly that would look nicer, but then we’d have no indication in browsers that don’t support box-shadows, such as IE8.
Once we’ve got those utilities we can define the main validation function, which tests the field and then performs the actual validation, if applicable: attribute to indicate that state – adding it to an invalid field that doesn’t already have it, or removing it from a valid field that does. Finally, to put this all into action, we need to bind the validation function to an . The smart way to do this is to (a) parse the date string with a regular expression, (b) construct a date object and (c) compare what you got out of the date object to what you put in. For legacy browsers that don’t implement these attributes, we can use their values as the basis of a polyfill.Regular Expressions (Regex): One of the most powerful, widely applicable, and sometimes intimidating techniques in software engineering.From validating email addresses to performing complex code refactors, regular expressions have a wide range of uses and are an essential entry in any software engineer's toolbox.
For instance, here is a basic regex that describes any time in the 24-hour HH/MM format. Most code editors support regex-based find/replace operations.