<p>无法将<code>f()</code>的本地<code>x</code>绑定到嵌套<code>g()</code>的全局变量<code>x</code>。为什么</p>
<pre><code>def f():
x=0
def g():
global x
x+=1
print(x)
g()
g() # added to make seemingly more practical
</code></pre>
<p>-</p>
<pre><code>>>> f()
...
NameError: global name 'x' is not defined
</code></pre>