Hint: Think: multiple queries done together means faster results [OK]
Common Mistakes:
Confusing speed with data storage
Thinking it improves single query quality
Assuming it deletes data automatically
2. Which of the following is the correct way to represent multiple queries for multi-query retrieval in Python?
easy
A. queries = ['query1', 'query2', 'query3']
B. queries = 'query1, query2, query3'
C. queries = {'query1': 1, 'query2': 2}
D. queries = query1 + query2 + query3
Solution
Step 1: Identify the correct data structure for multiple queries
Multiple queries should be stored as a list of strings to keep them separate.
Step 2: Check each option
queries = ['query1', 'query2', 'query3'] uses a list of strings, which is correct. queries = 'query1, query2, query3' is a single string, not multiple queries. queries = {'query1': 1, 'query2': 2} is a dictionary, which is not standard for query lists. queries = query1 + query2 + query3 tries to add strings, which concatenates them, not separate queries.
Final Answer:
queries = ['query1', 'query2', 'query3'] -> Option A
Quick Check:
List of strings = multiple queries [OK]
Hint: Use a list to hold multiple queries separately [OK]
Common Mistakes:
Using a single string instead of a list
Using a dictionary instead of a list
Concatenating queries into one string
3. Given the following Python code for multi-query retrieval, what will be the output?
queries = ['apple', 'banana']
results = {q: q.upper() for q in queries}
print(results)
medium
A. {'apple': 'APPLE', 'banana': 'BANANA'}
B. ['APPLE', 'BANANA']
C. {'APPLE': 'apple', 'BANANA': 'banana'}
D. Error: invalid syntax
Solution
Step 1: Understand the dictionary comprehension
The code creates a dictionary where each query string is a key, and its uppercase version is the value.
Step 2: Evaluate the comprehension for each query
For 'apple', the pair is 'apple': 'APPLE'; for 'banana', 'banana': 'BANANA'.
Final Answer:
{'apple': 'APPLE', 'banana': 'BANANA'} -> Option A
Quick Check:
Dict comprehension maps keys to uppercase values [OK]
Hint: Dict comprehension maps each query to its uppercase [OK]
Common Mistakes:
Confusing list output with dict output
Swapping keys and values
Thinking code has syntax error
4. Identify the error in this multi-query retrieval code snippet:
queries = ['cat', 'dog']
results = []
for q in queries:
results.append(q.upper)
print(results)
medium
A. Incorrect variable name 'q' in loop
B. Using list instead of dictionary for results
C. Missing parentheses after upper method call
D. Syntax error in for loop
Solution
Step 1: Check method usage in loop
The code calls q.upper without parentheses, so it references the method but does not call it.
Step 2: Understand the effect of missing parentheses
Appending q.upper adds the method object, not the uppercase string, causing unexpected results.
Final Answer:
Missing parentheses after upper method call -> Option C
Quick Check:
Method call needs () to execute [OK]
Hint: Remember to add () to call string methods like upper() [OK]
Common Mistakes:
Forgetting parentheses on method calls
Thinking list is wrong for storing results
Assuming variable name is incorrect
5. You want to retrieve results for multiple queries from a large dataset efficiently. Which approach best uses multi-query retrieval to improve speed and organize results?
hard
A. Run each query one after another and combine all results into one list
B. Run all queries at once and store each query's results separately in a dictionary
C. Run only the first query and ignore the rest to save time
D. Run queries randomly and merge results without labels
Solution
Step 1: Understand multi-query retrieval goal
It aims to run many queries simultaneously to save time and keep results organized.
Step 2: Evaluate options for efficiency and organization
Run all queries at once and store each query's results separately in a dictionary runs all queries at once and stores results separately, matching the goal. Run each query one after another and combine all results into one list runs queries one by one, slower. Run only the first query and ignore the rest to save time ignores queries, losing data. Run queries randomly and merge results without labels merges results without labels, losing clarity.
Final Answer:
Run all queries at once and store each query's results separately in a dictionary -> Option B
Quick Check:
Simultaneous queries + separate storage = efficient multi-query retrieval [OK]
Hint: Run all queries together and keep results labeled separately [OK]