An Introduction to Python Dictionary

What is a Python dictionary?

A Python dictionary is an unordered collection of key-value pairs. The keys are unique and can be any immutable data type, such as strings, numbers, or tuples. The values can be any data type, including other dictionaries.

Dictionaries are often used to store data that is related in some way. For example, you could use a dictionary to store the names and ages of your friends, or the prices of items in a store.

For example, this code creates a dictionary of names and ages:

```python

names_and_ages = {

    "John": 30,

    "Jane": 25,

    "Mike": 20

}

```

In this example, the keys are the names "John", "Jane", and "Mike", and the values are their ages, 30, 25, and 20, respectively.

Accessing dictionary items

You can access the items in a Python dictionary using the key. The key must be enclosed in square brackets [].

For example, this code gets the age of John from the dictionary above:

```python

john_age = names_and_ages["John"]

```

In this example, the variable `john_age` will be assigned the value `30`.

Updating dictionary items

You can update the value of a dictionary item by assigning a new value to the key.

For example, this code updates John's age to 31:

```python

names_and_ages["John"] = 31

```

Adding dictionary items

You can add new items to a dictionary by assigning a new key-value pair to the dictionary.

For example, this code adds a new entry to the dictionary for Mary, aged 22:

```python

names_and_ages["Mary"] = 22

```

Removing dictionary items

You can remove items from a dictionary using the `del` keyword.

For example, this code removes John from the dictionary:

```python

del names_and_ages["John"]

```

Iterating over dictionary items

You can iterate over the items in a dictionary using a for loop.

For example, this code prints the names and ages in the dictionary:

```python

for name, age in names_and_ages.items():

    print(name, age)

```

In this example, the loop will iterate over the keys and values in the dictionary, and print each key and value on a separate line.

Other dictionary methods

In addition to the methods mentioned above, Python dictionaries also have a number of other methods, such as:

- `len()`: Returns the number of items in the dictionary.

- `get()`: Returns the value for the given key, or None if the key does not exist.

- `keys()`: Returns a list of the keys in the dictionary.

- `values()`: Returns a list of the values in the dictionary.

- `items()`: Returns a list of key-value pairs in the dictionary.

Conclusion

Python dictionaries are a powerful data structure that can be used to store and retrieve data quickly and efficiently. They are a versatile tool that can be used in a wide variety of applications.

I hope this blog post has given you a good introduction to Python dictionaries.

Happy Coding!