Instruction
Finally, the last dictionary usage that we want to present is what's called linking.
Suppose we have an application whose behavior depends on the application settings. Application settings is a dictionary with key-value pairs. The application has some global defaults, but each user can fine-tune the settings in the user settings. Finally, user settings can be changed again on the project level. The picture below shows the different settings:
The value of "editor" parameter is "sublime", because that's its value in the project settings which has the highest precendence. The value of the parameter "timeout" is 500: it's not defined in the project settings, but it is defined in user settings.
Linking dictionaries in creating a new dictionary with the current parameter values based on existing dictionaries which are chained in a specific order. In this section we'll learn how to link dictionaries in Python.
The first function we'll need is very simple: the function copy(). It creates a copy of the dictionary. Take a look:
defaults = {'weight': 80.0, 'height': 1.82, 'age': 28.0}
user_profile = defaults.copy()
The user_profile is a copy of the dictionary defaults.
Exercise
You are given a dictionary with salaries for 2017. Create a copy of this salary and name it salaries_2018. In 2018 everyone got a 10% rise. Update the 2018 dictionary to reflect the rise – each value in salaries_2018 should be an integer.
Finally, print both dictionaries and observe that the values in the dictionary salaries_2017 were not modified. This confirms that salaries_2018 is a separate dictionary.
