Remove date limits imposed by Python's datetime module #27
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Permit processing and representation of years before 1 AD and after 999 AD by removing use of Pyhon's `datetime` and related modules, which are limited to these years. This changes the public API so the following methods return `struct_time` objects instead of `date` or `datetime` objects: `lower_strict()`, `upper_strict()`, `lower_fuzzy()`, `upper_fuzzy()` Details: - stop using `datetime` modules internally when parsing and processing EDTF syntax - change `_strict_date()` and all dependent methods to return `struct_time` instead of objects from the `datetime` module. This affects public API methods listed above - remove deliberate coercion of out-of-date year values to `date.min` and `date.max` boundaries - update tests to exercise broader date ranges
The `struct_time` fields tm_wday, tm_yday, tm_isdst are not supported by this library because we cannot reliably generate them for years outside 1 AD to 9999 AD, therefore we ignore these fields in comparison methods when a `struct_time` object is provided.
- explain the switch from `datetime` module objects to using `time.struct_time` as responses to upper/lower strict/fuzzy methods - update example code to reflect the change - remove reference to `date.MIN` and `date.MAX` restrictions.
The change to returning `struct_time` objects from the lower/upper strict/fuzzy methods broke the `EDTFField` implementation. This change fixes it so it can write to derived `DateField`s again, though this is still subject to the 1 to 9999 AD year restrictions of Python's `datetime` module so a better fix would be to support or require numeric target fields instead.
cogat
reviewed
Apr 13, 2018
edtf/parser/parser_classes.py
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"relativedelta" is redundant. Suggest apply_delta. Document what the op param is expected to be.
Fixed bug where target field was not properly looked-up, and therefore not recognised correctly.
Add the python module `jdutil` with many useful date conversions, including conversion from arbitrary dates/times to a numerical floating-point representation that can be easily stored in databases and other systems where we need easy and reliably sorting and comparison of arbitrary dates. Note that I chose this module over other library options available for Python because in my testing it did the best job of keeping accuracy for extreme dates (like year +-999,999,999) while also generating using a number that is easier to store than the two-float representation often used for Julian dates. Source: https://gist.github.com/jiffyclub/1294443 Credit to: Matt Davis, http://github.com/jiffyclub
Update `EDTFField` to store derived upper/lower static/float dates as float values when these fields are defined as `DoubleField` in the target model. This change permits representation of arbitrary dates not limited to 1 to 9999 AD like the alternative `DateField` target fields. Note that the stored value is not completely accurate and, in my testing, may drift by a few years for negative years in the thousands or millions – which seems like a reasonable limitation.
Unit test time conversion utilities, and fix a couple of bugs surfaced by tests.
Use a better name `edtf.convert` instead of `edtf.utils`
Add `struct_time_to_jd` and `jd_to_struct_time` functions to `edtf.convert` module to handle conversion to and from Julian Date numerical float values. These functions greatly simplify Julian Date (JD) conversions, especially for converting from JD values where fiddly handling may be required to convert negative month/day/hour/minute/second values returned by the `jdutil` module.
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See #26