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Learn to program with Python

Better way to get dictionary values #

When we try to get a dict value using a key that doesn't exist, Python raises a KeyError exception. This means that the key is not present in the dictionary, and the value cannot be accessed. And when an error happens, the program will stop running.

For example:

employee = {"name": "John", "age": 30, "position": "developer"}
gender = employee["gender"] # KeyError: 'gender'
print("Hello World!") # This will not run

A better way to get a dictionary value in Python is to use the get() method. The get() method returns the value for the specified key, but if the key is not found in the dictionary, it returns a default value instead of raising a KeyError. This can help avoid errors in case the key is not in the dictionary.

The syntax for get() method is:

dict.get(key, default_value)

where key is the key of the item you want to retrieve from the dictionary and default_value is the value that the method will return if the key is not found in the dictionary. If default_value is not specified, it defaults to None.

employee = {"name": "John", "age": 30, "position": "developer"}

# Accessing an existing key with get()
position = employee.get("position")
print(position) # Output: developer

# Accessing a non-existing key with get()
salary = employee.get("salary", 50000)
print(salary) # Output: 50000

# Accessing a non-existing key without default value
gender = employee.get("gender")
print(gender) # Output: None

In the example above, the get() method is used to retrieve the value for the "position" key from the employee dictionary. It returns "developer", since the value exists in the dictionary.

Then, the get() method is used again to retrieve the value for a non-existing "salary" key from the employee dictionary. Since the "salary" key does not exist, the method returns the default value of 50000.

The last get() method is called to get the value for the key "gender", which does not exist in the dictionary. But since we do not provide the default value, we get the value None as a default.

Exercise #

  • We have created a dictionary course_details. Use this dictionary and get() method to create following variables:
    • course_name to be the value of the key "name".
    • course_description to be the value of the key "description", but default to "Learn how to program in Python.".
    • course_stars to be the value of the key "stars". Do not provide a default value.

Tests #

  • Variable course_name should be "Python Programming"
  • Variable course_description should be "Learn how to program in Python."
  • Variable course_stars should be None
Output will be displayed here