ValueError：list.remove(x)：尝试使用 ElementTree 删除元素时 x 不在列表中

Question

我有一个 marc xml 文件，集合中有两条记录。我想从文件中删除 955 个数据字段。

当我尝试迭代由

findall

生成的列表时，我得到

ValueError

、

list.remove(x): x not in list

。

import xml.etree.ElementTree as ET
tree = ET.parse('toggle.xml')
root = tree.getroot()

for a955 in root.findall('record/datafield[@tag="955"]'):
    root.remove(a955)

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[1], line 6
      3 root = tree.getroot()
      5 for a955 in root.findall('record/datafield[@tag="955"]'):
----> 6     root.remove(a955)

ValueError: list.remove(x): x not in list

这是我正在尝试修改的 xml（为了简洁起见，我删除了一些数据字段）：

<collection>
    <record>
        <leader>00859cam a2200277Ia 4500</leader>
        <controlfield tag="005">20170510144913.0</controlfield>
        <controlfield tag="008">880930s1983    enka          00010 eng d</controlfield>
        <datafield tag="035" ind1=" " ind2=" ">
            <subfield code="a">ocm13279646 880930</subfield>
        </datafield>
        <datafield tag="035" ind1=" " ind2=" ">
            <subfield code="9">0674-46060</subfield>
        </datafield>
        <datafield tag="035" ind1=" " ind2=" ">
            <subfield code="a">(StEdNL)1580610-nlsdb-Voyager</subfield>
        </datafield>
        <datafield tag="700" ind1="1" ind2="0">
            <subfield code="a">Evans, Martin.</subfield>
        </datafield>
        <datafield tag="710" ind1="2" ind2="0">
            <subfield code="a">Health Education Council.</subfield>
            <subfield code="w">cn</subfield>
        </datafield>
        <datafield tag="710" ind1="2" ind2="0">
            <subfield code="a">Teachers' Advisory Council on Alcohol and Drug Education.</subfield>
        </datafield>
        <datafield tag="955" ind1=" " ind2=" ">
            <subfield code="a">QP4.88.1745</subfield>
            <subfield code="b">QP4DOT88DOT</subfield>
        </datafield>
        <datafield tag="956" ind1=" " ind2=" ">
            <subfield code="a">NLS</subfield>
        </datafield>
    </record>
    <record>
        <leader>01030cas a2200349 i 4500</leader>
        <controlfield tag="005">20190312175642.0</controlfield>
        <controlfield tag="008">130830c20139999stkwr ne      0   a0eng d</controlfield>
        <datafield tag="015" ind1=" " ind2=" ">
            <subfield code="a">GBB386135</subfield>
            <subfield code="2">bnb</subfield>
        </datafield>
        <datafield tag="022" ind1="1" ind2=" ">
            <subfield code="a">2053-6496</subfield>
        </datafield>
        <datafield tag="035" ind1=" " ind2=" ">
            <subfield code="a">(Uk)016484976</subfield>
        </datafield>
        <datafield tag="035" ind1=" " ind2=" ">
            <subfield code="a">2992934</subfield>
        </datafield>
        <datafield tag="035" ind1=" " ind2=" ">
            <subfield code="a">(StEdNL)5112576-nlsdb-Voyager</subfield>
        </datafield>
        <datafield tag="651" ind1=" " ind2="0">
            <subfield code="a">Troon (Scotland)</subfield>
            <subfield code="v">Newspapers.</subfield>
        </datafield>
        <datafield tag="651" ind1=" " ind2="0">
            <subfield code="a">South Ayrshire (Scotland)</subfield>
            <subfield code="v">Newspapers.</subfield>
        </datafield>
        <datafield tag="752" ind1=" " ind2=" ">
            <subfield code="a">Scotland</subfield>
            <subfield code="b">Strathclyde</subfield>
            <subfield code="d">Troon.</subfield>
            <subfield code="2">blnpn</subfield>
        </datafield>
        <datafield tag="919" ind1=" " ind2=" ">
            <subfield code="a">NBS</subfield>
        </datafield>
        <datafield tag="955" ind1=" " ind2=" ">
            <subfield code="y">2020</subfield>
            <subfield code="b">V000258858</subfield>
        </datafield>
    </record>
</collection>

我是基于

ElementTree docs

中的示例：

for country in root.findall('country'):
    # using root.findall() to avoid removal during traversal
    rank = int(country.find('rank').text)
    if rank > 50:
        root.remove(country)

我确信我做错了一些非常基本的事情，但我就是不知道它是什么。

Answer 1

根据文档：

remove(subelement)

从元素中删除子元素。

在这种情况下，子元素是 child。

remove

不会遍历整个树来查找您要求其删除的元素。

您选择的元素不是

root

（又名

collection

）的子元素，而是

record

的子元素。