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August 25, 2017 23:12
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| # Code example to manipulate dates (add days to dates) by parsing the string. | |
| # This is only useful when you cannot import datetime. | |
| def is_leap_year(year): | |
| if (year % 4 == 0 and year % 100 != 0) \ | |
| or (year % 400 is 0): | |
| return True | |
| else: | |
| return False | |
| def add_days_to_date(date_string, days_to_add): | |
| # J F M A M J J A S O N D | |
| days_per_month = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] | |
| day, month, year = map(int, date_string.split('/')) | |
| # February will have 29 days in leap years. | |
| days_per_month[1] = 29 if is_leap_year(year) else 28 | |
| day += days_to_add | |
| while day > days_per_month[month - 1]: | |
| day -= days_per_month[month - 1] | |
| month += 1 | |
| if month > 12: | |
| month -= 12 | |
| year += 1 | |
| days_per_month[1] = 29 if is_leap_year(year) else 28 | |
| # In case we are going backwards | |
| while day <= 0: | |
| month -= 1 | |
| if month <= 0: | |
| month += 12 | |
| year -= 1 | |
| days_per_month[1] = 29 if is_leap_year(year) else 28 | |
| day += days_per_month[month - 1] | |
| return '{:02}/{:02}/{}'.format(day, month, year) | |
| # To use it: | |
| metadata_value = add_days_to_date('01/01/1970', 10000) | |
| print(metadata_value) | |
| metadata_value = add_days_to_date('01/01/1970', -10000) | |
| print(metadata_value) | |
| # Just to test that it works | |
| tests = [('28/02/2017', 1, '01/03/2017'), | |
| ('28/02/2020', 1, '29/02/2020'), | |
| ('28/12/2017', 4, '01/01/2018'), | |
| ('01/01/2017', 31 + 28, '01/03/2017'), | |
| ('32/01/2017', 1, '02/02/2017'), | |
| ('01/01/2017', -1, '31/12/2016') | |
| ] | |
| for start_date, days_to_add, expected_result in tests: | |
| result = add_days_to_date(start_date, days_to_add) | |
| assert result == expected_result, \ | |
| "Expected '{}' but got '{}'".format(expected_result, result) |
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