Why unpack is so slowly?
<p>I have a simple example:</p>

<pre>
    def __init__(self,string):
        self.string = string

    def UI32(self):
        tmp = self.string[:4]
        self.string = self.string[4:]
        return unpack(">I",tmp)[0]

data = file.read()
U = UI(data)
for i in range(60000):
    test = UI32()
</pre>

<p>total time: 22 seconds !!!</p>
