POC Troubleshooting & Problem Resolution 5

Question 1

A `StopIteration` exception propagates out of a generator function unexpectedly. What Python version behavior causes this?

Accepted Answer

In Python 3.7+, StopIteration raised inside a generator is converted to RuntimeError

Answer

PEP 479 (active from Python 3.7) converts `StopIteration` raised inside a generator body into a `RuntimeError` to prevent silent bugs.

Question 2

You profile a slow script with `cProfile` and find most time is spent in a pure-Python loop. What is the best optimization?

Accepted Answer

Replace the loop with a NumPy vectorized operation or a built-in written in C

Answer

NumPy operations and built-in functions execute compiled C code, which is orders of magnitude faster than pure-Python loops.

Question 3

You get `ssl.SSLCertVerificationError` when making an HTTPS request. What is the secure resolution?

Accepted Answer

Update the CA certificates bundle used by Python or the requests library

Answer

Updating the CA bundle ensures Python can validate the server's certificate chain without disabling security.

Question 4

A long-running script leaks memory over time. `tracemalloc` shows many small string allocations in a loop. What is a likely culprit?

Accepted Answer

String concatenation with `+` inside a loop, creating a new object each iteration

Answer

Each `+` on strings creates a new immutable string object; accumulation inside a loop grows memory linearly.

Question 5

A subprocess call with `subprocess.run(['ls', '-l'])` works locally but raises `FileNotFoundError` on Windows. Why?

Accepted Answer

`ls` is a Unix command not available on Windows; use `dir` with `shell=True` on Windows

Answer

`ls` is a Unix shell command; Windows uses `dir`, and since it is a shell built-in, `shell=True` is required.

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