擅长:python、mysql、java
<p>您可以使用python计数器类来实现这一点。在</p>
<pre><code>from collections import counter
# creates a new Counter object
c = Counter()
# your file contents
lst_grades = "A A- C F C C B- B A A A- B B+ B+ B+ C C- B- A A A F"
# turn lst_grades to a list containing the grades
lst_grades = lst_grades.split(" ")
# printing lst_grades for a better idea what lst_grades looks like now
# lst_grades
# > ['A', 'A-', 'C', 'F', 'C', 'C', 'B-', 'B', 'A', 'A', 'A-', 'B', 'B+',
# 'B+', 'B+', 'C', 'C-', 'B-', 'A', 'A', 'A', 'F']
# call the update method of the counter c
# update takes an iterable (e.g. a list)
# and counts the values inside this iterable
c.update(lst_grades)
# now our counter contains a dictionary with the counted grads
# c
# > Counter({'A': 6, 'C': 4, 'B+': 3, 'B': 2, 'F': 2,
# 'B-': 2, 'A-': 2, 'C-': 1})
# you can simply access every counted entry
# c["A"]
# > 6
</code></pre>