Cisco 200-901 Practice Test

200-901 practice test: what's covered

• DevNet Associate
• 200-901

Free 200-901 sample questions

1. A team is choosing a data structure to store the latest unique IP addresses seen on the wire, where ordering does not matter and duplicate inserts must collapse silently. Which Python type is BEST?

   • A. Python list (ordered mutable sequence)
   • B. Python set (unordered collection of unique elements)
   • C. Python tuple (immutable ordered sequence)
   • D. Python dictionary with null value mappings
   Show answer

   Correct: B. set gives O(1) membership tests and automatic de-duplication — exactly the semantics described. list allows duplicates (the common trap). tuple is immutable and not deduplicating. A dict with None values works but wastes memory and intent compared with set.

2. Look at the snippet: <pre>def add(a, b=[]): b.append(a) return b print(add(1)) print(add(2))</pre> What is printed?

   • A. [1] followed by [2] on separate lines
   • B. [1] followed by [1, 2] on separate lines
   • C. TypeError raised on second function invocation
   • D. [1] followed by [1] on separate lines
   Show answer

   Correct: B. Mutable default arguments are evaluated ONCE at function-definition time and shared across calls — the classic Python gotcha. So b accumulates: [1] then [1,2]. The fix is `def add(a, b=None): b = b or []`. Believing each call gets a fresh [] is the trap distractor.

3. Which TWO statements about Git branching are TRUE? (Choose 2)

   • A. git commit (saves local staged changes to history)
   • B. git push (publishes local commits to remote repository)
   • C. git rebase (re-applies commits onto another base)
   • D. git status (displays working tree state)
   Show answer

   Correct: A and B. rebase replays commits on a new base — that IS rewriting history. pull = fetch + merge (or rebase). merge can fast-forward without a merge commit (use --no-ff to force one). cherry-pick COPIES a commit (the source still has it). stash SAVES changes for later, it does not delete them.

4. A class manages a database connection. To make sure the connection is always closed even on exceptions, what is the CLEANEST Python pattern?

   • A. Wrap every call site in try/except/finally
   • B. Implement __enter__ and __exit__ so the class can be used as a context manager via `with`
   • C. Override __del__ to close on garbage collection
   • D. Use a global atexit handler
   Show answer

   Correct: B. Context managers are the idiomatic Python pattern — `with conn:` guarantees __exit__ runs on normal exit and exceptions. __del__ is unreliable because GC timing is not guaranteed. try/finally works but repeats at every call site. atexit only runs at interpreter shutdown.

5. Which design pattern describes a single shared instance used to provide one global access point, often used for configuration objects?

   • A. Factory Pattern
   • B. Singleton Pattern
   • C. Observer Pattern
   • D. Strategy Pattern
   Show answer

   Correct: B. Singleton enforces a single instance with a global access point — the textbook pattern for shared configuration or logging. Factory creates instances. Observer is publish/subscribe. Strategy swaps interchangeable algorithms.

Last updated: 2026-09-23

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