scriptconfig.smartcast module

scriptconfig.smartcast.smartcast(item, astype=None, strict=False, allow_split=False)[source]

Converts a string into a standard python type.

In many cases this is a simple alternative to eval. However, the syntax rules use here are more permissive and forgiving.

The astype can be specified to provide a type hint, otherwise we try to cast to the following types in this order: int, float, complex, bool, none, list, tuple.

Parameters:

  • item (str | object) – represents some data of another type.

  • astype (type | None) – if None, try infer what the best type is, if astype == ‘eval’ then try to return eval(item), Otherwise, try to cast to this type. Default to None.

  • strict (bool) – if True raises a TypeError if conversion fails. Default to False.

  • allow_split (bool) – if True will interpret strings with commas as sequences. Defaults to True.

Returns:

some item

Return type:

object

Raises:

TypeError – if we cannot determine the type

Example

>>> # Simple cases
>>> print(repr(smartcast('?')))
>>> print(repr(smartcast('1')))
>>> print(repr(smartcast('1,2,3')))
>>> print(repr(smartcast('abc')))
>>> print(repr(smartcast('[1,2,3,4]')))
>>> print(repr(smartcast('foo.py,/etc/conf.txt,/baz/biz,blah')))
'?'
1
[1, 2, 3]
'abc'
[1, 2, 3, 4]
['foo.py', '/etc/conf.txt', '/baz/biz', 'blah']

>>> # Weird cases
>>> print(repr(smartcast('[1],2,abc,4')))
['[1]', 2, 'abc', 4]

Example

>>> assert smartcast('?') == '?'
>>> assert smartcast('1') == 1
>>> assert smartcast('1.0') == 1.0
>>> assert smartcast('1.2') == 1.2
>>> assert smartcast('True') is True
>>> assert smartcast('false') is False
>>> assert smartcast('None') is None
>>> assert smartcast('1', str) == '1'
>>> assert smartcast('1', eval) == 1
>>> assert smartcast('1', bool) is True
>>> assert smartcast('[1,2]', eval) == [1, 2]

Example

>>> def check_typed_value(item, want, astype=None):
>>>     got = smartcast(item, astype)
>>>     assert got == want and isinstance(got, type(want)), (
>>>         'Cast {!r} to {!r}, but got {!r}'.format(item, want, got))
>>> check_typed_value('?', '?')
>>> check_typed_value('1', 1)
>>> check_typed_value('1.0', 1.0)
>>> check_typed_value('1.2', 1.2)
>>> check_typed_value('True', True)
>>> check_typed_value('None', None)
>>> check_typed_value('1', 1, int)
>>> check_typed_value('1', True, bool)
>>> check_typed_value('1', 1.0, float)
>>> check_typed_value(1, 1.0, float)
>>> check_typed_value(1.0, 1.0)
>>> check_typed_value([1.0], (1.0,), 'tuple')