'dict' object has no attribute 'has_key'

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

python python-3.x dictionary

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'))

python python-3.x dictionary

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)>> Trueprint('E' in graph)>> False

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