为什么布尔（xml.etree.ElementTree.Element）评价为False？ [英] Why does bool(xml.etree.ElementTree.Element) evaluate to False?

问题描述

import xml.etree.ElementTree as ET
e = ET.Element('Brock',Role="Bodyguard")
print bool(e)

为什么是 xml.etree.ElementTree.Element 认为假？

我知道我能做到如果e不是无来检查是否存在。但我的强烈期望布尔（E）返回真。

I know that I can do if e is not None to check for existence. But I would strongly expect bool(e) to return True.

推荐答案

事实证明，元素对象被认为是一个假价值，如果他们没有孩子。

As it turns out, Element objects are considered a False value if they have no children.

我发现这个源：

def __nonzero__(self):
    warnings.warn(
        "The behavior of this method will change in future versions.  "
        "Use specific 'len(elem)' or 'elem is not None' test instead.",
        FutureWarning, stacklevel=2
        )
    return len(self._children) != 0 # emulate old behaviour, for now

即使是行内注释同意你 - 这种行为是前途未卜;）

Even the inline comment agrees with you -- this behavior is iffy ;)

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