removing null values from a dictionary

I recently was converting a Python dictionary to a JSON object to include in the body of a POST request. Unfortunately, this triggered a response from the service I was sending the data too:

{
  "Code": "InvalidInputValue",
  "Message": "Cannot perform operation because the value doesn't match the data type of the following field(s): Date_Client_Received"
}

This is because my dictionary had a null value that I hadn’t removed. Knowing the issue, we can now solve it.

Assuming for the moment that we don’t have control over what goes into the dictionary, we have two approaches

1. Dictionary Comprehension (works well if the dictionary is not nested)
2. Recursive “cleaning”

Approach One: Dictionary Comprehension

def remove_none_values(dict):
    """
    Given a dictionary, dict, remove None values
    If a dictionary includes nested values, a recursive approach is required
    """
    return {
        key:value
        for key, value in dict.items()
        if value is not None
    }

Approach Two: Recursive Cleaning

Similar to the dictionary comprehension, we need to look at each key in the dictionary and, if it’s None, remove it. However, in this case, if a value is another dictionary, we can dive into that key as well to remove None values.

def remove_none_values(dict):
    """
    Given a dictionary, dict, remove None values
    If the dictionary includes nested dictionaries, investigate and remove None values there too.
    """
    cleaned_dict = {}
    for key, value in dict.items():
        if isinstance(value, dict):
            nested_dict = remove_non_values(value)
            if len(nested_dict.keys()) > 0:
                cleaned_dict[key] = nested_dict
        elif value is not None:
            cleaned_dict[key] = value
    return cleaned_dict

Conclusion

Here are two ways to clean a dictionary of empty keys - the latter which can handle nested dictionaries. This can helpful if you need to send along the dictionary to another service that may not be able to handle a None value.