'dict' object has no attribute 'has_key'

Question

While traversing a graph in Python, a I\'m receiving this error:

\'dict\' object has no attribute \'has_key\'

Here is my code:

Answer 1

Try:

if start not in graph:

For more info see ProgrammerSought

Answer 2

In python3, has_key(key) is replaced by __contains__(key)

Tested in python3.7:

a = {'a':1, 'b':2, 'c':3}
print(a.__contains__('a'))

Answer 3

I think it is considered "more pythonic" to just use in when determining if a key already exists, as in

if start not in graph:
    return None

Answer 4

has_key has been deprecated in Python 3.0. Alternatively you can use 'in'

graph={'A':['B','C'],
   'B':['C','D']}

print('A' in graph)
>> True

print('E' in graph)
>> False

Answer 5

has_key was removed in Python 3. From the documentation:

• Removed dict.has_key() – use the in operator instead.

Here's an example:

if start not in graph:
    return None

Answer 6

The whole code in the document will be:

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

After that, the code you will run in the Python IDLE shell will be:

find_path(graph, 'A','D')

The answer you should receive in IDLE is

['A', 'B', 'C', 'D']