python - 判断是否在字典里用in还是用has_key()

Question

这两个都是一样的结果呢

z = {'a': 1, 'b': 2, 'c':3}
'a' in z
z.has_key('a')

Answer 1

Official documentation recommends using key in dict syntax because it is shorter and easier to understand. has_key is an old legacy API, left behind to support code before 2.2. This function has been removed in Python3.

Answer 2

The information above is detailed enough, so I’ll just post some code:

#src/Python-2.6.8/Objects/dictobject.c

static PyObject *
dict_has_key(register PyDictObject *mp, PyObject *key)
{
    if (PyErr_WarnPy3k("dict.has_key() not supported in 3.x; "
                       "use the in operator", 1) < 0) 
        return NULL;
    return dict_contains(mp, key);
}

Answer 3

is the same, in has a more pythonic feel, has_key has been removed in python3: http://docs.python.org/3.1/whatsnew/3...