小编Ste*_*ist的帖子

如何从其构造函数中设置ElementTree Element的文本字段？或者,在下面的代码中,为什么root.text的第二次打印无？

import xml.etree.ElementTree as ET

root = ET.fromstring("<period units='months'>6</period>")
ET.dump(root)
print root.text

root=ET.Element('period', {'units': 'months'}, text='6')
ET.dump(root)
print root.text

root=ET.Element('period', {'units': 'months'})
root.text = '6'
ET.dump(root)
print root.text

这里输出:

<period units="months">6</period>
6
<period text="6" units="months" />
None
<period units="months">6</period>
6

我从python.org unittest文档中逐字复制了这个:

import random
import unittest

class TestSequenceFunctions(unittest.TestCase):

    def setUp(self):
        self.seq = range(10)

    def test_shuffle(self):
        # make sure the shuffled sequence does not lose any elements
        random.shuffle(self.seq)
        self.seq.sort()
        self.assertEqual(self.seq, range(10))

        # should raise an exception for an immutable sequence
        self.assertRaises(TypeError, random.shuffle, (1,2,3))

    def test_choice(self):
        element = random.choice(self.seq)
        self.assertTrue(element in self.seq)

    def test_sample(self):
        with self.assertRaises(ValueError):
            random.sample(self.seq, 20)
        for element in random.sample(self.seq, 5):
            self.assertTrue(element in self.seq)

if __name__ == '__main__':
    unittest.main()

但是我从linux2上的python 2.7.2 [GCC 4.1.2 20080704(Red Hat 4.1.2-51)]中得到了这个错误信息:

.E.
======================================================================
ERROR: test_sample …