Intermediate · Dictionaries · 138 of 264
Average per student
Read scores; a student can appear several times. Print each student's average with one decimal, students in alphabetical order.
Input: n, then n lines "name score". Output: one line per student: <name> <average>
Examples
Input
4 ann 90 bob 70 ann 80 bob 75
Output
ann 85.0 bob 72.5
Input
1 zed 100
Output
zed 100.0
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().