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Streaming and Generators Theory Quiz

Question 1

In Python, what is an iterable?

  • A file that has already been fully loaded into memory
  • An object that Python can loop over
  • A function that must use return
  • A variable that stores only numbers

Answer: 2 Type: single Time: 45 Explanation: An iterable is something Python can loop over, such as a list, string, file, or generator.

Question 2

What does an iterator remember?

  • Its current position in a sequence
  • Every possible future value
  • The total memory used by Python
  • The name of the source file only

Answer: 1 Type: single Time: 45 Explanation: An iterator remembers where it is, so repeated calls to next() move forward through the values.

Question 3

Which statements about file iteration are correct? Select two.

  • A file loop always stores all lines in a list first
  • Looping over a file reads one line at a time
  • readlines() is required before every file loop
  • A file object can be used with iter() and next()

Answer: 2,4 Type: multiple Time: 60 Explanation: Files can be streamed line by line, and file objects are iterable. readlines() loads all lines and is not required for looping.

Question 4

For the task "print only the first line of a large file", which strategy is usually best?

  • Load all lines with readlines()
  • Sort the file first
  • Compare every line with every other line
  • Stream the file and read one line

Answer: 4 Type: single Time: 45 Explanation: Only the first line is needed, so streaming avoids unnecessary memory use.

Question 5

Which tasks usually require loading all selected data into memory? Select two.

  • Sort every line alphabetically
  • Access line 10,000 many times
  • Print only the first line
  • Count all lines

Answer: 1,2 Type: multiple Time: 60 Explanation: Sorting needs the lines together, and repeated random access is easier after loading. First-line printing and counting can stream.

Question 6

What does yield do in a generator function?

  • It stops the program immediately
  • It creates a list containing all results
  • It gives one value, pauses the function, and can continue later
  • It imports data from Hugging Face

Answer: 3 Type: single Time: 50 Explanation: yield produces one value at a time and keeps the function state for the next request.

Question 7

Which statements about yield and return are correct? Select two.

  • yield always makes the time complexity O(1)
  • return gives back one final value and stops the function
  • return automatically streams a file line by line
  • yield can produce a sequence of values over time

Answer: 2,4 Type: multiple Time: 60 Explanation: return ends the function, while yield lets a generator produce values one at a time. yield does not magically make all work constant time.

Question 8

You count all lines in a file by looping over the file and keeping only a counter.

What is the extra space complexity?

  • O(n), because all lines must be stored
  • O(log n), because the file is searched
  • O(1), ignoring the current line buffer
  • O(n²), because the file has many lines

Answer: 3 Type: single Time: 50 Explanation: The program keeps a fixed number of variables, so the extra space is constant apart from the current line being read.

Question 9

You search for the first line containing "Jean Valjean" and stop with break when it is found.

Which statements are correct? Select two.

  • break forces Python to read the rest of the file
  • The best case can be fast if the match is near the start
  • The worst case may still check every line
  • This task always needs readlines()

Answer: 2,3 Type: multiple Time: 60 Explanation: break lets the search stop early, but if the match is late or missing, the loop may inspect the whole file.

Question 10

A generator yields non-empty lines from a very large text file. Another loop counts how many yielded lines contain "Jean".

Which complexity description is most accurate?

  • Time is always O(1), because generators use yield
  • Space is always O(n), because generators store every yielded value
  • The program must load all lines before it can count
  • Time can be O(total characters checked), and extra space can stay small

Answer: 4 Type: single Time: 70 Explanation: The program may still inspect many characters, but it can avoid storing the whole file by processing one yielded line at a time.