defaultdict

`defaultdict` is a subclass of the built-in `dict` class from the `collections` module. It provides a convenient way to handle missing keys by automatically assigning a default value when accessing a key that doesn't exist in the dictionary.

To use `defaultdict`, you need to import it from the `collections` module. Here's an example:


from collections import defaultdict

fruit_prices = defaultdict(lambda: "Unknown")
fruit_prices["apple"] = 1.0
fruit_prices["banana"] = 0.5

print(fruit_prices["apple"])  # Output: 1.0
print(fruit_prices["banana"])  # Output: 0.5
print(fruit_prices["orange"])  # Output: Unknown
1.0
0.5
Unknown

In this code, we create a `defaultdict` object called `fruit_prices` with a default value of `"Unknown"`. We assign prices for `"apple"` and `"banana"`, but when we access the price for `"orange"`, which is not present in the dictionary, the default value `"Unknown"` is returned.

The default value is specified as a lambda function in this example, but you can use any callable object e.g. `list`, `dict` or a function that doesn't require any arguments.

The benefit of using `defaultdict` is that it eliminates the need for explicit checks and handling of missing keys. When accessing a missing key, it automatically creates the key with the default value assigned to it.

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