Question

我正在使用python模块lxml和psutil来记录一些系统指标，这些指标要放在XML文件中并复制到远程服务器，以便通过php进行解析并显示给用户。

然而，lxml在将一些变量，对象等推送到我的XML的各个部分时给了我一些麻烦。

例如：

import psutil, os, time, sys, platform
from lxml import etree

# This creates <metrics>
root = etree.Element('metrics')

# and <basic>, to display basic information about the server
child1 = etree.SubElement(root, 'basic')

# First system/hostname, so we know what machine this is
etree.SubElement(child1, "name").text = socket.gethostname()

# Then boot time, to get the time the system was booted.
etree.SubElement(child1, "boottime").text = psutil.boot_time()

# and process count, see how many processes are running.
etree.SubElement(child1, "proccount").text = len(psutil.pids())

获取系统主机名的行。

然而接下来的两行用于获取启动时间和进程计数错误，用：

>>> etree.SubElement(child1, "boottime").text = psutil.boot_time()
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "lxml.etree.pyx", line 921, in lxml.etree._Element.text.__set__ (src/lxml/lxml.etree.c:41344)
 File "apihelpers.pxi", line 660, in lxml.etree._setNodeText (src/lxml/lxml.etree.c:18894)
 File "apihelpers.pxi", line 1333, in lxml.etree._utf8 (src/lxml/lxml.etree.c:24601)
 TypeError: Argument must be bytes or unicode, got 'float'
>>> etree.SubElement(child1, "proccount").text = len(psutil.pids())
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "lxml.etree.pyx", line 921, in lxml.etree._Element.text.__set__ (src/lxml/lxml.etree.c:41344)
 File "apihelpers.pxi", line 660, in lxml.etree._setNodeText (src/lxml/lxml.etree.c:18894)
 File "apihelpers.pxi", line 1333, in lxml.etree._utf8 (src/lxml/lxml.etree.c:24601)
 TypeError: Argument must be bytes or unicode, got 'int'

所以，这就是我的XML在打印时的样子：

>>> print(etree.tostring(root, pretty_print=True))
<metrics>
  <basic>
    <name>mercury</name>
    <boottime/>
    <proccount/>
  </basic>
</metrics>

那么，无论如何将浮动和整数推送到我需要的xml文本中吗？或者我完全错了吗？

感谢您提供的任何帮助。

Answer 1

text字段应为unicode或str，而不是任何其他类型（boot_time为float，len()为int）。因此，只需将非字符串兼容元素转换为字符串：

# First system/hostname, so we know what machine this is
etree.SubElement(child1, "name").text = socket.gethostname() # nothing to do

# Then boot time, to get the time the system was booted.
etree.SubElement(child1, "boottime").text = str(psutil.boot_time())

# and process count, see how many processes are running.
etree.SubElement(child1, "proccount").text = str(len(psutil.pids()))

结果：

b'<metrics>\n  <basic>\n    <name>JOTD64</name>\n    <boottime>1473903558.0</boottime>\n    <proccount>121</proccount>\n  </basic>\n</metrics>\n'

我认为库可以进行isinstance(str,x)测试或str转换，但它不是那样设计的（如果你想用前导零，截断的小数显示你的浮点数怎么办...）。如果lib假定所有内容都是str，那么它的运行速度会更快。

Python使用lxml编写带有系统性能数据的xml文件

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