The comprehension shape works for dicts and sets too, and it can choose a value for each item instead of filtering.

words = ["tea", "milk", "tea", "jam"]
lengths = {w: len(w) for w in words}
firsts = {w[0] for w in words}
sizes = ["big" if len(w) > 3 else "small"
         for w in words]
print(lengths)
print(sorted(firsts))  # ['j', 'm', 't']
print(sizes)

• A trailing if filters: items that fail it are left out.
• a if condition else b before the for picks a value for every item, so the result has one entry per input.
• Two for clauses run like nested loops, outer first: [(r, c) for r in range(2) for c in range(3)].
• Round brackets give a generator expression, which feeds sum, any, all, min and max without building a list.

nums = [3, 8, 12]
print(any(n > 10 for n in nums))  # True
print(all(n > 0 for n in nums))   # True

When a comprehension needs several conditions and a nested loop, a plain for loop is easier to read.

Write price_index(pairs) turning a list of (name, price) tuples into a dict from name to price, leaving out prices of 0 or less. Write labels(scores) returning a list with "pass" for each score of at least 50 and "fail" for the others.

The explanation opens here once every check passes.