Identify which outer or nested object changed.
Review list identity, shallow copies, dictionary updates and defaults, set size and filtered comprehensions.
This count checks matching outcomes on six supplied CPython 3.14.5 tasks. It is not a developer band, percentile, employer threshold or qualification. Every worked answer and all four complete guides remain available at every count.
Count containers separately from their contents
These six tasks follow ordinary lists, dictionaries and sets, with every relevant operation visible. Assigning another name to a list differs from making a shallow outer copy. Replacing a dictionary value differs from inserting another key. A missing-key get can return a fallback without changing that dictionary. The set item counts retained members, while the comprehension filters values before transforming them. None of the questions requires guessing a set’s display order.
A copied outer list can share an inner dictionary
In a new unscored example, source is [{"n":1}]. Make copy with source.copy(), then set copy[0]["n"] to 3. The outer lists are distinct, but their first elements reach the same dictionary. Printing source[0]["n"] and source is copy with a colon gives 3:False. Draw the dictionary once and connect both outer positions to it. Merely drawing two outer lists does not establish independent nested data.
Track assignment and copy as different events
When alias receives source directly, both names refer to one list, so appending through either name affects the same contents. A shallow copy instead creates a new outer list whose elements initially refer to the original element objects. Mutation of a shared inner object can remain visible from both sides. That does not mean every change to either outer list is shared. Identify precisely which list or nested value the shown assignment modifies.
Distinguish an update from a fallback lookup
Writing to an existing equal key replaces its value rather than keeping two historical entries for that key. Calling get on a missing key with a supplied default returns that default without inserting an entry. Keep a small two-column record of keys and current values before checking the length. Do not substitute subscription or a different dictionary method while predicting this code; those alternatives can have different failure or insertion behaviour.
Apply the predicate before the expression
The comprehension starts from its stated range, keeps only values satisfying the remainder test and squares those selected values in order. The later join converts numbers to strings and supplies the punctuation that is actually printed. A set length asks a different question: how many distinct supplied string values survive. Neither operation is a sorting request. List brackets or an assumed set order should not be added to a printed joined string.
Predict the source after each operation
Use invented values in a new disposable .py file. For a shallow copy, predict the outer identity and one nested mutation separately. For a dictionary lookup, predict both the returned value and the entry count. Change one feature at a time and write the prediction before running with the declared interpreter. Keep real customer data, useful files and application state outside this exercise; no upload or access to those materials is needed on the website.
Review the particular data operation
A missed key may reflect confusion about aliasing, a fallback value or a filter boundary. The six-item count cannot distinguish those causes and does not assess managing a production dataset or preventing every unwanted mutation. Read all worked explanations and try new values after learning the fixed key. No rank, hiring recommendation, ability tier or certification is supplied. All four full guides remain available at every count after a valid complete attempt.