Reading broken code

Code that runs perfectly happily and gives the wrong answer. Professionals spend far more time reading and diagnosing than writing, and almost no tutorial practices it — so here the code is already written, and the job is working out why it is wrong.

8 exercisesdifficulty 2–4~165 min in total

—Exercises 8 exercises

The basket that adds up to almost rightdebug float equality, tolerance ~20 min The leaderboard where 9 beats 100debug sort keys, strings that look like numbers ~20 min 'int' object is not callabledebug shadowing a built-in, name lookup order ~18 min The basket that remembersdebug default arguments, when defaults are evaluated ~20 min The snippet that is short at one end and wrong at the otherdebug exclusive slice ends, negative indices wrap ~22 min The cleanup that crashes halfway throughdebug mutating while iterating, build rather than delete ~20 min The filter that misses every other onedebug iterating while modifying, how for walks a list ~20 min Three discount buttons, one discountdebug closures, late binding ~25 min