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’))