CODEWITHSUNDEEP
pythonpython-3.xdictionary
Ashi
Ashi

Reputation: 2189

'dict' object has no attribute 'has_key'

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

'dict' object has no attribute 'has_key'

Here is my code:

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

Why am I getting this error and how can I fix it?

Upvotes: 218

Views: 311223

Answers (6)

Godfrey
Godfrey

Reputation: 1101

Try:

if start not in graph:

For more info see ProgrammerSought

Upvotes: 7

qloveshmily
qloveshmily

Reputation: 1051

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'))

Upvotes: 68

Abhishek Pansotra
Abhishek Pansotra

Reputation: 1017

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

Upvotes: 33

Oana Roxana
Oana Roxana

Reputation: 41

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']

Upvotes: 4

johnnyRose
johnnyRose

Reputation: 7490

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

Upvotes: 325

Kevin S
Kevin S

Reputation: 2803

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

Upvotes: 9

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