擅长:python、mysql、java
<p>修改<code>if</code>:</p>
<pre><code>if digit == '':
if len(output)==0:
print('The input was blank')
break
else:
print(output, 'is a valid hexadecimal string.')
break
elif digit not in hexadecimal:
print(digit, 'is not a valid hexadecimal digit.')
break
</code></pre>