'KeyError' occurs when you try to access a dictionary key that doesn't exist. Use the `get()` method to provide a default value, or check for the key's existence using the `in` keyword.

'KeyError' is a common exception in Python that arises when you attempt to access a key in a dictionary that does not exist. This often happens when there’s an assumption that a key is present without verifying its existence first. To prevent KeyErrors, you can use the get() method, which allows you to specify a default value to return if the key is not found. For example, value = my_dict.get('key', default_value) will return default_value instead of raising a KeyError if 'key' is not present. Another approach is to check for the key’s existence using the in keyword before attempting to access it, like this: if 'key' in my_dict:. This proactive checking can help you avoid KeyErrors altogether. If you frequently need to handle missing keys, consider using collections.defaultdict, which automatically initializes a key with a default value if it is not found. By implementing these strategies, you can effectively manage and prevent KeyErrors in your Python applications.