Note: since this answer keeps getting upvoted - while there are still use cases for TypedDict, I'd consider using a dataclass instead today.

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I want to have a nice (`mypy --strict` and pythonic) way to turn an untyped `dict` (from `json.loads()`) into a `TypedDict`. My current approach looks like this:

class BackupData(TypedDict, total=False):
    archive_name: str
    archive_size: int
    transfer_size: int
    transfer_time: float
    error: str


def to_backup_data(data: Mapping[str, Any]) -> BackupData:
    result = BackupData()
    if 'archive_name' in data:
        result['archive_name'] = str(data['archive_name'])
    if 'archive_size' in data:
        result['archive_size'] = int(data['archive_size'])
    if 'transfer_size' in data:
        result['transfer_size'] = int(data['transfer_size'])
    if 'transfer_time' in data:
        result['transfer_time'] = int(data['transfer_time'])
    if 'error' in data:
        result['error'] = str(data['error'])
    return result

i.e I have a TypedDict with optional keys and want a TypedDict instance.

The code above is redundant and non-functional (in terms of functional programming) because I have to write names four times, types twice and result has to be mutable. Sadly TypedDict can't have methods otherwise I could write s.th. like

backup_data = BackupData.from(json.loads({...}))

Is there something I'm missing regarding TypeDict? Can this be written in a nice, non-redundant way?