Timestamp Functions |
In HL7 messages, fields that contain date and time information store it in the following format:
YYYY[MM[DD[HHmm[SS[.SSSS]]]]][zZZZZ] |
This is interpreted as follows:
- YYYY is a 4-digit year;
- MM and DD are the month and day;
- HH and mm are the hour and minute;
- SS.SSSS is the second, with up to four decimal places of accuracy (ten-thousandths of a second);
- zZZZZ is the time zone offset (z is either + or -).
- The square brackets [] indicate components of the timestamp that are optional. Everything other than the YYYY is optional: you can specify a year, a year and month, a year, month and day, and so on.
The following are all valid date/time formats:
YYYY YYYYMM YYYYMMDD YYYYMMDDHHmm YYYYMMDDHHmmSS YYYYMMDDHHmmSS.SSSS YYYYMMDDHHmmSS.SSSSzZZZZ |
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If you specify the hour (HH), you must also specify the minute (mm). The time zone offset can be specified even if any of the other fields are missing. | ||
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A date/time representation in any of these valid formats is known as a timestamp.
To make it easier for you to use timestamps in your Python scripts, Chameleon defines functions that create, process and validate timestamps. The following functions are defined:
| Function | Description |
|---|---|
| make_timestamp() | Returns a timestamp using the current time. The timestamp is returned in YYYYMMDDHHmmSS.SSSS format. Each call to make_timestamp() always returns a unique value (the same timestamp is never returned twice). |
| is_timestamp(timestamp) | Returns true if timestamp is a valid timestamp, and false otherwise. A timestamp is only valid if it is in the correct format and its values make sense. See below for an example. |
| parse_timestamp(timestamp) | Parses a timestamp and returns its components as a list consisting of the following elements: year, month, day, hour, minute, second, fraction of a second, plus or minus timezone offset. If the timestamp is not valid, a ValueError exception is raised. See below for details on how fractions of a second are returned by parse_timestamp(). |
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New Feature in Iguana 4.1.13 These functions were added to version 4.1.13 of Iguana. | ||
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To use these functions, you must import the ifware.timestamp module. For example:
from ifware.timestamp import * timestamp = make_timestamp() |
The is_timestamp() function performs two types of validation: it checks whether the timestamp is in the proper format, and it checks whether each component of the timestamp is meaningful. For example, the following timestamp is flagged as invalid:
20100332144761 |
While this timestamp is in the proper format, some of its fields contain values that are not meaningful: the DD (day) field is 32, and the SS (seconds) field is 61. is_timestamp() would flag this timestamp as invalid.
Note that parse_timestamp() returns fractions of a second as a decimal fraction (for example, .25 represents a quarter of a second). To return the number of ten-thousandths of a second in the timestamp, you will need to multiply the returned fraction by 10000:
(Y, M, D, h, m, s, fraction, tz) = parse_timestamp(timestamp) tts = int(fraction*10000) # tts contains the number of 10000ths of a second |