How Does Extracting Of a Value From Dictionary Work?

Question

sampleDict = {
  "name": "Kelly",
  "age":25,
  "salary": 8000,
  "city": "New york"
}

keys = ["name", "salary"]
newDict = { k: sampleDict[k] for k in keys}

print(newDict)

What are you trying to extract here?? Can you show us the expected output? — Ajay A, Jan 06 '21 at 10:02
Are you asking how sampleDict[k] returns the appropriate value? — Niteya Shah, Jan 06 '21 at 10:04
What is your question? The new dictionary is generated using [dictionary comprehension](https://stackoverflow.com/questions/14507591/python-dictionary-comprehension), where the keys you've given it "transfers" the key/value pairs to a new dictionary. — MatsLindh, Jan 06 '21 at 10:05
Maybe [this](https://stackoverflow.com/questions/1747817/create-a-dictionary-with-list-comprehension) helps? — costaparas, Jan 06 '21 at 10:07
To `extract` values from a Python dictionary, you have to provide the key, e.g., `print(newDict["name"])` should print `"Kelly"` — anurag, Jan 06 '21 at 10:16

score 1 · Answer 1 · answered Jan 06 '21 at 10:08

It might be clearer what's happening if you avoid using dictionary comprehension (where the loop happens inside {}.

The new dictionary is generated by { k: sampleDict[k] for k in keys}, but we can rewrite that to be more explicit:

sample_dict = {"name": "Kelly", "age":25, "salary": 8000, "city": "New york"}
keys_to_keep = ["name", "salary"]
new_dict = {}

for key in keys_to_keep:
    new_dict[key] = sample_dict[key]

print(new_dict)

In effect, for each key referenced in keys_to_keep, copy the existing value from sample_dict and store it under the same key in new_dict.

How Does Extracting Of a Value From Dictionary Work?

1 Answers1