word_lengths[word] = len(word)
return word_lengths
I do not understand the solution provided in this exercise. Why/how does word_lengths[word] = len(word) add a new key?
Because that’s the way (well, one way) that you add a new key to a dictionary. If word is not already a key, word_lengths[word] = len(word) will add it, with the associated value len(word).
If word it is already a key, the statement word_lengths[word] = something will overwrite the current value with whatever is on the right side of the assignment statement.
my_dict = {}
word = "ant"
my_dict[word] = len(word)
print(my_dict)
my_dict[word] = len(word) * 2 # Different value here so you can see a change
print(my_dict)
my_dict[word] += 10 # This is more interesting!
print(my_dict)
Output:
{'ant': 3}
{'ant': 6}
{'ant': 16}
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