擅长:python、mysql、java
<p>使用<a href="http://docs.python.org/2/tutorial/datastructures.html?highlight=dictionary%20comprehension#dictionaries" rel="nofollow">dictionary comprehension</a>:</p>
<pre><code>def distribution(filename):
'string ==> int & string, prints out how many students got a letter grade'
infile = open(filename,'r')
grades = infile.read().split('\n')
# this creates a list of the grades, without the new-line character
infile.close()
possible_grades = ('A', 'A-', 'B', 'B-', 'C', 'C-', 'D', 'D-', 'F')
gradesDict = {i:grades.count(i) for i in possible_grades}
for x in gradesDict.keys():
print(x + ':', gradesDict[x])
</code></pre>