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# pandas.api.extensions.ExtensionDtype.construct_from_string¶

classmethod ExtensionDtype.construct_from_string(string: str)[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: string : str The name of the type, for example category. ExtensionDtype Instance of the dtype. TypeError If a class cannot be constructed from this ‘string’.

Examples

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

>>> @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("Cannot construct a '{}' from "
...                         "'{}'".format(cls.__name__, string))

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