when can I use dot notation to access a dictionary in Python

I am modifying somebody's code in the context of the 'gym'' environment and came across the use of the dot notation to access a dictionary. the following snippet shows that the dictionary in gym can use the notation but when I duplicate it it throws an error.

import gym
env = gym.Env
env = make('connectx', debug=True)
config = env.configuration
print(config)
print(config.timeout)
dct = {'timeout': 5, 'columns': 7, 'rows': 6, 'inarow': 4, 'steps': 1000}
print(dct.timeout)

this provides the following output:

{'timeout': 5, 'columns': 7, 'rows': 6, 'inarow': 4, 'steps': 1000}
5

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
   <ipython-input-45-674d59d34c55> in <module>
      6 print(config.timeout)
      7 dct = {'timeout': 5, 'columns': 7, 'rows': 6, 'inarow': 4, 'steps': 1000}
----> 8 print(dct.timeout)

AttributeError: 'dict' object has no attribute 'timeout'

I am using Python 3. Can somebody explain please? Thanks

Solution 1:

Unlike JavaScript objects, Python dicts don't natively support dot notation.

Try Dotsi, Addict or a similar library. Here's a quick snippet of Dotsi in action:

>>> import dotsi
>>> 
>>> d = dotsi.Dict({"foo": {"bar": "baz"}})     # Basic
>>> d.foo.bar
'baz'
>>> d.users = [{"id": 0, "name": "Alice"}]      # In list
>>> d.users[0].name
'Alice'
>>> 

Disclosure: I'm Dotsi's author.

Solution 2:

In python you cannot access a dictionnary value with dict.key, you need to use dict[key]

Example :

d = {"foo": 2}
print(d["foo"])
# 2

key = foo
print(d[key])
# 2

print(d.foo)
# AttributeError: 'dict' object has no attribute 'foo'

print(d.key)
# AttributeError: 'dict' object has no attribute 'key'

If you really want to use the dot notation, you can use a class (your config is probably a class instance by the way):

class MyClass():
    def __init__(self):
        self.foo = "bar"

a = MyClass()
print(a.foo)
# bar