擅长:python、mysql、java
<p>如果我没弄错的话,你想要这样的东西:</p>
<pre><code>import math
def area(a, b=None):
if b is None:
# b not specified:
x = math.pi * a**2
else:
# b specified:
x = math.pi * a*b
return x
def main():
print("First", area(7))
print("Second", area(5, 4))
main()
</code></pre>
<p>输出为</p>
<pre><code>First 153.93804002589985
Second 62.83185307179586
</code></pre>
<p>如果未指定<code>b</code>,则将其设置为<code>None</code>。然后在函数中进行测试</p>
<p>它在原始示例中打印<code>(153.93804002589985, 0.0)</code>的原因是您使用<code>return x,y</code>从函数返回一个元组<code>(x, y)</code></p>