python - 当我运行 `for glyph in font.iter(' glyph')` 时，为什么 etree 没有从我的 SVG 中返回任何内容？

Question

目标

我是 Python 的新手。我想我会尝试编写一个脚本，使用 etree 从 SVG 图标文件中检索 glyph-name 和 unicode 以从中创建一个 LESS 文件。

暴力解决方案

我编写了一个解决方案，在该解决方案中，我遍历 SVG 元素以获取元素属性，将它们放入列表中，然后根据列表中的属性编写我的 LESS 样式。它看起来像这样:

SVG结构

<?xml version="1.0" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><!--
2019-3-13: Created with FontForge (http://fontforge.org)
-->
<svg xmlns="http://www.w3.org/2000/svg" 
    xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1">
    <metadata>
Created by FontForge 20170731 at Wed Mar 13 07:05:16 2019 By root
    </metadata>
    <defs>
        <font id="Flaticon" horiz-adv-x="512">
            <font-face font-family="Flaticon" font-weight="400" font-stretch="normal" units-per-em="512" panose-1="2 0 5 3 0 0 0 0 0 0" ascent="448" descent="-64" bbox="-0.00048785 -64.001 512 448" underline-thickness="25.6" underline-position="-51.2" unicode-range="U+0020-F131" />
            <missing-glyph />
            <glyph glyph-name="space" unicode=" " horiz-adv-x="200" />
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v-18.1338h34.7002z" />
        </font>
    </defs>
</svg>

from lxml import etree

filename = "font.svg"
tree = etree.parse(open(filename, 'r'))

# Brute Force Method: Iterate through everything and then iterate through attributes.
for element in tree.iter():
    attributes = []

    for name, value in element.attrib.items():
        if (name == "glyph-name") or (name == "unicode"):
            attributes.insert(0, value)

    if type(attributes) != 'bool' and len(attributes) == 2:

        lessPreStyle += '''\
            .icon-{name} {{
                &:before {{
                    content: {unicode};
                }}
            }}
            '''.format(name=attributes[0], unicode=repr(attributes[1]).replace('\\u', '\\'))

优雅的解决方案

现在我试图通过仅遍历字形而不是每个元素并直接从对象获取属性而不是遍历属性来检查它是否被称为 glyph-name 或 unicode。到目前为止，我有这样的事情:

# Go directly to the parent of the glyphs
font = tree.getroot()[1][0]

# Filter only glyphs
for glyph in font.iter('glyph'):
    print (glyph.attrib['unicode'])
    print (glyph.attrib['glyph-name'])

我当前的问题是 for glyph in font.iter('glyph') 不返回任何内容。根据Python 3.6.8 Documentation我应该能够通过在 iter() 函数中输入我想要的子元素的名称来过滤子元素。但是，我什么也没得到。如果我删除过滤器并只打印子项的标签名称，我将获得所有标签名称。我不想像上次那样迭代和检查单个元素。我在这里错过了什么吗？或者是否有更好的方法来实现相同的目标？

Answer 1

您的 SVG 有一个默认命名空间 (http://www.w3.org/2000/svg)。

要在 iter() 中指定命名空间，您必须使用 Clark Notation。这基本上是命名空间 uri 和本地名称的组合:{http://www.w3.org/2000/svg}glyph

您还可以使用 * 而不是实际的命名空间 uri 来匹配任何命名空间中的元素:{*}glyph

参见 here和 here了解更多信息。

例子:

from lxml import etree

tree = etree.parse("font.svg")

# Filter only glyphs
for glyph in tree.iter('{http://www.w3.org/2000/svg}glyph'):
    print(glyph.attrib['unicode'])
    print(glyph.attrib['glyph-name'])