问题描述
在 Python 中，list += x 似乎适用于任何可迭代的 x:
在[6]中:l = []在 [7] 中:l += [1]在 [8] 中:l += (2, 3)在 [9] 中: l += xrange(5)在[10]中:l输出[10]:[1、2、3、0、1、2、3、4]这种行为是否记录在任何地方?
为了与 list + x 进行对比，后者仅在 x 也是 list 时才有效.这在 文档.
来自 Guido van Rossum:p><块引用>
它的工作方式与 .extend() 相同，只是它也返回 self.一世找不到解释这一点的文档.:-(
这里是取自 listobject.c:
list_inplace_concat(PyListObject *self, PyObject *other){PyObject *结果；结果 = 列表扩展(自我，其他)；如果(结果 == NULL)返回结果；Py_DECREF(结果)；Py_INCREF(自我)；返回(PyObject *)自我；}我已提交错误报告以修复文档:http://bugs.python.org/issue16701
It would appear that in Python, list += x works for any iterable x:
In [6]: l = []
In [7]: l += [1]
In [8]: l += (2, 3)
In [9]: l += xrange(5)
In [10]: l
Out[10]: [1, 2, 3, 0, 1, 2, 3, 4]
Is this behaviour documented anywhere?
To contrast this with list + x, the latter only works if x is also a list. This is spelled out in the documentation.
From Guido van Rossum:
It works the same way as
.extend()except that it also returnsself. I can't find docs explaining this. :-(
Here is the relevant source code taken from listobject.c:
list_inplace_concat(PyListObject *self, PyObject *other)
{
PyObject *result;
result = listextend(self, other);
if (result == NULL)
return result;
Py_DECREF(result);
Py_INCREF(self);
return (PyObject *)self;
}
I've raised a bug report to have the documentation fixed: http://bugs.python.org/issue16701
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