pandas.api.extensions.ExtensionDtype.construct_from_string#

classmethod ExtensionDtype.construct_from_string(string)[source]#

Construct this type from a string.

This is useful mainly for data types that accept parameters. For example, a period dtype accepts a frequency parameter that can be set as period[H] (where H means hourly frequency).

By default, in the abstract class, just the name of the type is expected. But subclasses can overwrite this method to accept parameters.

Parameters:

stringstr: The name of the type, for example category.

Returns:

ExtensionDtype: Instance of the dtype.

Raises:

TypeError: If a class cannot be constructed from this ‘string’.

Examples

For extension dtypes with arguments the following may be an adequate implementation.

>>> import re
>>> @classmethod
... def construct_from_string(cls, string):
...     pattern = re.compile(r"^my_type\[(?P<arg_name>.+)\]$")
...     match = pattern.match(string)
...     if match:
...         return cls(**match.groupdict())
...     else:
...         raise TypeError(
...             f"Cannot construct a '{cls.__name__}' from '{string}'"
...         )