Suppose we have the following Python code:

s = {"apple": 1, "banana": 2}

t = {"coconut": 3, "durian": 4}

How would you append the key-value pairs of t to s?

(the updated s should be: {"apple": 1, "banana": 2, "coconut": 3, "durian": 4})

Question

Suppose we have the following Python code:

s = {"apple": 1, "banana": 2}

t = {"coconut": 3, "durian": 4}

How would you append the key-value pairs of t to s?

(the updated s should be: {"apple": 1, "banana": 2, "coconut": 3, "durian": 4})

BlackTom AI · Accepted Answer

The dict method update merges key-value pairs from another mapping into the dictionary, so s.update(t) is the correct operation.

1) Relevant knowledge points and concepts
- Python dictionaries are mutable mappings of keys to values.
- dict.update(other) takes another mapping (or iterable of key-value pairs) and adds/overwrites key-value pairs into the dictionary in place.
- There is no dict.add or dict.append method, and you cannot use the + operator to concatenate dictionaries in Python versions prior to 3.9 (and even in 3.9+ the operator merges but returns a new dict, not modify in place).

2) Complete reasoning process step by step
- Starting state: s = {"apple": 1, "banana": 2}, t = {"coconut": 3, "durian": 4}.
- We want s to contain the keys/values from t as well.
- Using s.update(t) tells Python: take every key/value in t and insert into s, overwriting any existing keys if there are duplicates.

3) Intermediate steps / demonstration
- s = {"apple": 1, "banana": 2}
- t = {"coconut": 3, "durian": 4}
- s.update(t)   # modifies s in place
- After update, s is {"apple": 1, "banana": 2, "coconut": 3, "durian": 4}
- Note: s.update(t) returns None, so do not assign its result back to s (i.e., don't do s = s.update(t)).

4) Why the correct answer is correct
- update is the dictionary method specifically designed to append/merge key-value pairs from another mapping into the existing dictionary, producing the exact desired result.

5) Why other options are incorrect
- s.add(t): dict has no add method (sets have add).
- s.append(t): append is a list method; dicts have no append.
- s + t: invalid for dicts (TypeError in most versions); it does not perform in-place merging.
- None of above: incorrect because a valid option exists.

6) Conclusion
The correct choice is s.update(t), which matches the provided answer.

Suppose we have the following Python code: s = {"apple": 1, "banana": 2} t = {"coconut": 3, "durian": 4} How would you append the key-value pairs of t to s? (the updated s should be: {"apple": 1, "banana": 2, "coconut": 3, "durian": 4})单项选择题

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