'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:

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

6 Answers

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 

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')) 

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 

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 

Try:

if start not in graph: 

For more info see ProgrammerSought

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']