Idioms that mark you as fluent

Loop like a local

These idioms exist because Python is read far more often than it is written: teams standardize on them, reviewers expect them, and interviewers quietly grade on them. Each one replaces bookkeeping with stated intent.

Three rewrites cover most unpythonic loops.

Need the index too? enumerate, never range(len(...)):

for i, word in enumerate(words, start=1):
    print(i, word)

Two sequences in step? zip:

for name, score in zip(names, scores):
    print(name, score)

Multiple assignment by unpacking:

low, high = high, low        # swap, no temp variable
first, *rest = [1, 2, 3, 4]  # first=1, rest=[2, 3, 4]

And truthiness: empty string, empty list, empty dict, 0, and None are all falsy, so write if items: rather than if len(items) > 0:. One exception: to distinguish None from empty, compare is None explicitly, as in the lesson 2-2 sentinel.

Small habits, big readability

• Chained comparisons: if 0 <= i < len(xs): reads like math and replaces two clauses joined by and.
• f-strings for all formatting: f"{price:.2f}" renders 2 decimal places, f"{count:>5}" right-aligns in 5 columns.
• dict.get(key, default) instead of checking in before reading.
• EAFP ("easier to ask forgiveness than permission"): Python style prefers trying the operation and catching the specific exception (lesson 8-3) over pre-checking every condition.

None of these change what your program can do. They change how fast the next human, often future you, can read it. That is worth real money in code review.