Coding classes for adults in Canada

<!doctype html>
<html lang="en-CA">
<head>
  <meta charset="utf-8">
  <title>Riverside Rink Volunteers: winter schedule</title>
</head>
<body>
  <h1>Riverside Rink Volunteers</h1>
  <img src="rink.jpg" alt="The outdoor rink at dusk, lights on">
  <img src="logo.png">
  <form>
    <label for="email">Email for shift reminders</label>
    <input id="email" type="email">
    <input type="text" placeholder="Your name">
    <button>Sign me up</button>
  </form>
</body>
</html>

The first image has alternative text and the email box has a label. The logo image has no alt attribute, and the name box relies on placeholder text instead of a label, which disappears as soon as someone types.

# Our accessibility spot-check for one HTML file (a project from our adult web course)
from html.parser import HTMLParser
import sys

class Checker(HTMLParser):
    def __init__(self):
        super().__init__()
        self.problems = []
        self.labelled = set()      # ids that a <label for="..."> points at
        self.inputs = []           # (id, type) of every <input>
        self.has_title = False
        self.lang = None

    def handle_starttag(self, tag, attrs):
        a = dict(attrs)
        if tag == "html":
            self.lang = a.get("lang")
        elif tag == "title":
            self.has_title = True
        elif tag == "img" and "alt" not in a:
            self.problems.append("image without alt text: " + a.get("src", "?"))
        elif tag == "label" and "for" in a:
            self.labelled.add(a["for"])
        elif tag == "input":
            self.inputs.append((a.get("id"), a.get("type", "text")))

    def report(self):
        if not self.lang:
            self.problems.append("no lang attribute on <html>")
        if not self.has_title:
            self.problems.append("no <title>")
        for input_id, kind in self.inputs:
            if input_id not in self.labelled:
                self.problems.append("input without a label: type=" + kind)
        return self.problems

checker = Checker()
with open(sys.argv[1], encoding="utf-8") as page:
    checker.feed(page.read())
problems = checker.report()
for p in problems:
    print("FIX:", p)
print(len(problems), "problem(s) found")

It uses only Python's standard library (html.parser), so there is nothing to install. It checks for a lang attribute, a title, alt text on every image and a label for every input.

$ python check_page.py index.html
FIX: image without alt text: logo.png
FIX: input without a label: type=text
2 problem(s) found