擅长:python、mysql、java
<p><code>eval</code>方法用于返回值,不用于执行string命令,只接受一行命令</p>
<p>要执行string命令,需要<code>exec</code>方法,下面是正确的代码</p>
<pre><code>counterc = 0
countern = 0
counterx = 0
letter = input()
if letter in ['c','n','x']:
exec('counter' + letter + '=' + 1)
</code></pre>