擅长:python、mysql、java
<p>在python中,函数的默认返回值是<code>None</code>。</p>
<pre><code>>>> def func():pass
>>> print func() #print or print() prints the return Value
None
>>> func() #remove print and the returned value is not printed.
>>>
</code></pre>
<p>所以,只要使用:</p>
<p><code>letter_grade(score) #remove the print</code></p>
<p>另一种选择是用<code>return</code>替换所有打印:</p>
<pre><code>def letter_grade(score):
if 90 <= score <= 100:
return "A"
elif 80 <= score <= 89:
return "B"
elif 70 <= score <= 79:
return "C"
elif 60 <= score <= 69:
return "D"
elif score < 60:
return "F"
else:
#This is returned if all other conditions aren't satisfied
return "Invalid Marks"
</code></pre>
<p>现在使用<code>print()</code>:</p>
<pre><code>>>> print(letter_grade(91))
A
>>> print(letter_grade(45))
F
>>> print(letter_grade(75))
C
>>> print letter_grade(1000)
Invalid Marks
</code></pre>