Here is an example of how you can create a dictionary that contains keys and values.

#!/usr/bin/python
dictionary = {
  "foo": "Hello",
  "bar": "World"
}
print(dictionary)

Which should print the following.

{'foo': 'Hello', 'bar': 'World'}

Here is how you could replace "Hello" with "Goodbye" in the "foo" key.

#!/usr/bin/python3
dictionary = {
  "foo": "Hello",
  "bar": "World"
}

dictionary['foo'] = "Goodbye"

print(dictionary)

Which should now print the following.

{'foo': 'Goodbye', 'bar': 'World'}

And like this, with nested keys.

#!/usr/bin/python3
dictionary = {
  "foo": {
    "bar": {
      "hello": "world"
    }
  }
}

print(dictionary)

dictionary['foo']['bar']['hello'] = "Saturn"

print(dictionary)