What's the difference between _b and b in this place
<pre><code>class a:
    def __init__(self):
        self._b()#why here use _b,not b,What's the difference
        self._c='cccc'#why here use _c,not c,What's the difference
    def _b():
        print 'bbbb'
</code></pre>

<p>a.py</p>

<pre><code>class a:
    def __init__(self):
        self._b()#why here use _b,not b,What's the difference
        self._c='cccc'#why here use _c,not c,What's the difference
    def _b(self):
        print 'bbbb'
</code></pre>

<p>b.py</p>

<pre><code>from  a import *
b=a()
b._b()
print b._c
</code></pre>

<p>it print 
bbbb
bbbb
bbbb
bbbb
cccc</p>

<p>Why can print out these, aren't _b and _c private variables.</p>
