Python “dict”对象没有属性“has_key”
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'dict' object has no attribute 'has_key'
提问by Ashi
While traversing a graph in Python, a I'm receiving this error:
在 Python 中遍历图形时，我收到此错误：
'dict' object has no attribute 'has_key'
“dict”对象没有属性“has_key”
Here is my code:
这是我的代码：
def find_path(graph, start, end, path=[]):
path = path + [start]
if start == end:
return path
if not graph.has_key(start):
return None
for node in graph[start]:
if node not in path:
newpath = find_path(graph, node, end, path)
if newpath: return newpath
return None
The code aims to find the paths from one node to others. Code source: http://cs.mwsu.edu/~terry/courses/4883/lectures/graphs.html
该代码旨在找到从一个节点到其他节点的路径。代码来源：http: //cs.mwsu.edu/~terry/courses/4883/lectures/graphs.html
Why am I getting this error and how can I fix it?
为什么我会收到此错误，我该如何解决？
回答by johnnyRose
has_keywas removed in Python 3. From the documentation:
has_key已在 Python 3 中删除。从文档中：
- Removed
dict.has_key()– use theinoperator instead.
- 已删除
dict.has_key()- 改用in运算符。
Here's an example:
下面是一个例子：
if start not in graph:
return None
回答by Kevin S
I think it is considered "more pythonic" to just use inwhen determining if a key already exists, as in
我认为仅in在确定密钥是否已存在时才使用它被认为是“更 Pythonic” ，如
if start not in graph:
return None
回答by Oana Roxana
The whole code in the document will be:
文档中的整个代码将是：
graph = {'A': ['B', 'C'],
'B': ['C', 'D'],
'C': ['D'],
'D': ['C'],
'E': ['F'],
'F': ['C']}
def find_path(graph, start, end, path=[]):
path = path + [start]
if start == end:
return path
if start not in graph:
return None
for node in graph[start]:
if node not in path:
newpath = find_path(graph, node, end, path)
if newpath: return newpath
return None
After writing it, save the document and press F 5
写完后，保存文档并按F 5
After that, the code you will run in the Python IDLE shell will be:
之后，您将在 Python IDLE shell 中运行的代码将是：
find_path(graph, 'A','D')
find_path（图形，'A'，'D'）
The answer you should receive in IDLE is
您应该在 IDLE 中收到的答案是
['A', 'B', 'C', 'D']
回答by Abhishek Pansotra
has_keyhas been deprecated in Python 3.0. Alternatively you can use 'in'
has_key在Python 3.0 中已被弃用。或者，您可以使用“in”
graph={'A':['B','C'],
'B':['C','D']}
print('A' in graph)
>> True
print('E' in graph)
>> False
回答by qloveshmily
In python3, has_key(key)is replaced by __contains__(key)
在python3中，has_key(key)被替换为__contains__(key)
Tested in python3.7:
在python3.7中测试：
a = {'a':1, 'b':2, 'c':3}
print(a.__contains__('a'))
