Intermediate · Dictionaries · 140 of 264
First unique letter
Find the first character that appears only once in a word.
Input: a word. Output: that character, or none
Examples
Input
swiss
Output
w
Input
aabb
Output
none
Input
abc
Output
a
One more test checks other inputs when you press Check.
Stuck? The idea behind dictionaries
A dictionary links keys to values, like words to meanings: ages["Ann"] = 12. Looking up a key is fast, however big it is.
.get(key, 0) gives a default when the key isn't there; looping over a dictionary gives its keys, .items() gives keys and values together.
counts = {}
for word in input().split():
counts[word] = counts.get(word, 0) + 1
for word, n in counts.items():
print(word, n)Watch for: Reading a key that isn't there stops the program with a KeyError: check with in, or use .get().