Dictionary

What are Python dictionaries?

Python dictionaries are unordered collections of key-value pairs. This means that each item in a dictionary has a key and a value, and the keys must be unique. Dictionaries are created using curly braces ({}) and can contain any type of data, including integers, floats, strings, lists, and dictionaries.

How to create a Python dictionary

To create a Python dictionary, you simply enclose the key-value pairs in curly braces. For example:

Python

my_dictionary = {"name": "John Doe", "age": 30}
 

This code creates a dictionary with two key-value pairs: name and age. The key name is associated with the value John Doe, and the key age is associated with the value 30.

How to access items in a Python dictionary

To access items in a Python dictionary, you use the square bracket operator ([]) and the key of the item. For example:

Python

print(my_dictionary["name"])  # Outputs "John Doe"
print(my_dictionary["age"])  # Outputs 30
 

You can also use the get() method to access items in a dictionary. The get() method takes the key of the item as its argument and returns the value of the item, or None if the key is not in the dictionary. For example:

Python

my_dictionary["occupation"] = "Software Engineer"

print(my_dictionary.get("occupation"))  # Outputs "Software Engineer"
print(my_dictionary.get("hobbies"))  # Outputs None
 

How to iterate over a Python dictionary

To iterate over a Python dictionary, you can use the for loop. The for loop iterates over each key in the dictionary and executes a block of code for each key. For example:

Python

for key in my_dictionary:
  print(my_dictionary[key])
 

This code will print the value of each key in the dictionary to the console.

Python dictionary methods

There are a few Python dictionary methods that can be used to perform various tasks on dictionaries, such as adding and removing items from a dictionary, checking if a key is in a dictionary, and getting the keys and values of a dictionary.

Here are some examples of Python dictionary methods:

• update(other_dictionary): Updates the dictionary with the key-value pairs from the other dictionary.
• pop(key): Removes the specified key-value pair from the dictionary and returns the value.
• clear(): Removes all items from the dictionary.
• keys(): Returns a list of all the keys in the dictionary.
• values(): Returns a list of all the values in the dictionary.

Here are some additional tips for using Python dictionaries:

• Use descriptive variable names for your dictionaries. This will make your code more readable and easier to maintain.
• Add comments to your code to explain what your dictionaries are used for. This will help other developers understand your code and make it easier to debug.
• Dictionaries are a good choice for storing data that needs to be associated with keys.
• Use the isinstance() function to check the data type of a variable before using it as a dictionary. This can help you to avoid errors.