擅长:python、mysql、java
<p>如果要在一个通道中计算流入和流出,可以使用以下结构:</p>
<pre><code>from collections import Counter
last_char = None
my_list = "aaabbaccba"
inflow = Counter()
outflow = Counter()
for char in my_list:
inflow[char] += 1
if last_char and char != last_char:
outflow[last_char] += 1
last_char = char
print(inflow)
print(outflow)
</code></pre>
<p>它输出:</p>
<pre><code>Counter({'a': 5, 'b': 3, 'c': 2})
Counter({'a': 2, 'b': 2, 'c': 1})
</code></pre>
<p>注意,对于<a href="https://docs.python.org/2/library/collections.html#collections.Counter" rel="nofollow noreferrer">^{<cd1>}</a>,您不需要<code>setdefault</code>。你知道吗</p>