ciso8601

ciso8601 converts ISO 8601 or RFC 3339 date time strings into Python datetime objects.

Since it's written as a C module, it is much faster than other Python libraries. Tested with Python 2.7, 3.4, 3.5, 3.6, 3.7, 3.8.

Note: ciso8601 doesn't support the entirety of the ISO 8601 spec, only a popular subset.

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Contents

Quick Start

% pip install ciso8601

In [1]: import ciso8601

In [2]: ciso8601.parse_datetime('2014-12-05T12:30:45.123456-05:30')
Out[2]: datetime.datetime(2014, 12, 5, 12, 30, 45, 123456, tzinfo=pytz.FixedOffset(330))

In [3]: ciso8601.parse_datetime('20141205T123045')
Out[3]: datetime.datetime(2014, 12, 5, 12, 30, 45)

Migration to v2

Version 2.0.0 of ciso8601 changed the core implementation. This was not entirely backwards compatible, and care should be taken when migrating See CHANGELOG for the Migration Guide.

Error Handling

Starting in v2.0.0, ciso8601 offers strong guarantees when it comes to parsing strings.

parse_datetime(dt: String): datetime is a function that takes a string and either:

• Returns a properly parsed Python datetime, if and only if the entire string conforms to the supported subset of ISO 8601
• Raises a ValueError with a description of the reason why the string doesn't conform to the supported subset of ISO 8601

If time zone information is provided, an aware datetime object will be returned. Otherwise, a naive datetime is returned.

Benchmark

Parsing a timestamp with no time zone information (ex. 2014-01-09T21:48:00):

Module	Python 3.8	Python 3.7	Python 3.6	Python 3.5	Python 3.4	Python 2.7	Relative Slowdown (versus ciso8601, Python 3.8)
ciso8601	201 nsec	157 nsec	160 nsec	139 nsec	148 nsec	147 nsec	N/A
pendulum	215 nsec	232 nsec	234 nsec	205 nsec	192 nsec	9.44 usec	1.1x
udatetime	906 nsec	1.06 usec	767 nsec	702 nsec	819 nsec	923 nsec	4.5x
str2date	5.96 usec	7.75 usec	7.27 usec	6.84 usec	7.6 usec	Incorrect Result (None)	29.7x
isodate	10.3 usec	10 usec	11.1 usec	11.9 usec	12.3 usec	43.6 usec	51.3x
iso8601utils	10.3 usec	8.63 usec	9.16 usec	10.3 usec	9.58 usec	11.1 usec	51.5x
iso8601	10.9 usec	11.1 usec	10.5 usec	11.2 usec	11.5 usec	25.6 usec	54.2x
PySO8601	13.9 usec	21.9 usec	20.2 usec	15.9 usec	23.7 usec	16.4 usec	69.4x
aniso8601	14.5 usec	15 usec	15.8 usec	15.9 usec	16.1 usec	17.2 usec	72.5x
zulu	25.3 usec	29.9 usec	28.2 usec	27.4 usec	33 usec	N/A	126.3x
maya	42.9 usec	57.4 usec	58.2 usec	67.5 usec	87.6 usec	100 usec	213.7x
arrow	85.7 usec	81.8 usec	75.7 usec	78.7 usec	N/A	93.9 usec	427.1x
python-dateutil	122 usec	82.7 usec	72.2 usec	77.1 usec	74.4 usec	131 usec	609.5x
moment	3.81 msec	4.46 msec	3.12 msec	3.66 msec	N/A	3.59 msec	19011.9x

ciso8601 takes 201 nsec, which is 1.1x faster than pendulum, the next fastest ISO 8601 parser in this comparison.

Parsing a timestamp with time zone information (ex. 2014-01-09T21:48:00-05:30):

Module	Python 3.8	Python 3.7	Python 3.6	Python 3.5	Python 3.4	Python 2.7	Relative Slowdown (versus ciso8601, Python 3.8)
ciso8601	207 nsec	219 nsec	282 nsec	262 nsec	264 nsec	360 nsec	N/A
pendulum	249 nsec	225 nsec	209 nsec	212 nsec	209 nsec	12.9 usec	1.2x
udatetime	806 nsec	866 nsec	817 nsec	827 nsec	792 nsec	835 nsec	3.9x
str2date	7.57 usec	10.7 usec	7.98 usec	8.48 usec	9.06 usec	Incorrect Result (None)	36.7x
isodate	12 usec	13.5 usec	14.7 usec	15.4 usec	18.8 usec	47.6 usec	58.3x
iso8601	12.8 usec	14.6 usec	14.6 usec	15.2 usec	17.7 usec	30 usec	61.8x
aniso8601	19.4 usec	30.4 usec	22.1 usec	20.5 usec	21.9 usec	20.1 usec	94.0x
iso8601utils	22.5 usec	25.3 usec	26.4 usec	25.7 usec	27 usec	26.9 usec	108.9x
zulu	25.6 usec	31.2 usec	30 usec	32.3 usec	30.7 usec	N/A	124.1x
PySO8601	25.9 usec	35.4 usec	25.6 usec	29.5 usec	27.7 usec	25.7 usec	125.2x
maya	48.5 usec	46.6 usec	51.3 usec	63.2 usec	68.1 usec	125 usec	234.9x
python-dateutil	79.3 usec	88.5 usec	101 usec	89.8 usec	91.9 usec	160 usec	384.2x
arrow	86.2 usec	95.2 usec	95 usec	101 usec	N/A	103 usec	417.2x
moment	Incorrect Result (None)	Incorrect Result (None)	Incorrect Result (None)	Incorrect Result (None)	N/A	Incorrect Result (None)	3442935.3x

ciso8601 takes 207 nsec, which is 1.2x faster than pendulum, the next fastest ISO 8601 parser in this comparison.

Tested on Darwin 18.7.0 using the following modules:

aniso8601==8.0.0
arrow==0.15.2
ciso8601==2.1.2
iso8601==0.1.12
iso8601utils==0.1.2
isodate==0.6.0
maya==0.6.1
moment==0.8.2
pendulum==2.0.5
PySO8601==0.2.0
python-dateutil==2.8.0
str2date==0.905
udatetime==0.0.16
zulu==1.1.1

Note: ciso8601 doesn't support the entirety of the ISO 8601 spec, only a popular subset.

For full benchmarking details (or to run the benchmark yourself), see benchmarking/README.rst

Dependency on pytz (Python 2)

In Python 2, ciso8601 uses the pytz library while parsing timestamps with time zone information. This means that if you wish to parse such timestamps, you must first install pytz:

pip install pytz

Otherwise, ciso8601 will raise an exception when you try to parse a timestamp with time zone information:

In [2]: ciso8601.parse_datetime('2014-12-05T12:30:45.123456-05:30')
Out[2]: ImportError: Cannot parse a timestamp with time zone information without the pytz dependency. Install it with `pip install pytz`.

pytz is intentionally not an explicit dependency of ciso8601. This is because many users use ciso8601 to parse only naive timestamps, and therefore don't need this extra dependency. In Python 3, ciso8601 makes use of the built-in datetime.timezone class instead, so pytz is not necessary.

Supported Subset of ISO 8601

ciso8601 only supports the most common subset of ISO 8601.

Date Formats

The following date formats are supported:

Format	Example	Supported
YYYY-MM-DD	2018-04-29	✅
YYYY-MM	2018-04	✅
YYYYMMDD	2018-04	✅
--MM-DD (omitted year)	--04-29	❌
--MMDD (omitted year)	--0429	❌
±YYYYY-MM (>4 digit year)	+10000-04	❌
+YYYY-MM (leading +)	+2018-04	❌
-YYYY-MM (negative -)	-2018-04	❌

Week dates or ordinal dates are not currently supported.

Format	Example	Supported
YYYY-Www (week date)	2009-W01	❌
YYYYWww (week date)	2009W01	❌
YYYY-Www-D (week date)	2009-W01-1	❌
YYYYWwwD (week date)	2009-W01-1	❌
YYYY-DDD (ordinal date)	1981-095	❌
YYYYDDD (ordinal date)	1981095	❌

Time Formats

Times are optional and are separated from the date by the letter T.

Consistent with RFC 3339, ciso860 also allows either a space character, or a lower-case t, to be used instead of a T.

The following time formats are supported:

Format	Example	Supported
hh	11	✅
hhmm	1130	✅
hh:mm	11:30	✅
hhmmss	113059	✅
hh:mm:ss	11:30:59	✅
hhmmss.ssssss	113059.123456	✅
hh:mm:ss.ssssss	11:30:59.123456	✅
hhmmss,ssssss	113059,123456	✅
hh:mm:ss,ssssss	11:30:59,123456	✅
Midnight (special case)	24:00:00	✅
hh.hhh (fractional hours)	11.5	❌
hh:mm.mmm (fractional minutes)	11:30.5	❌

Note: Python datetime objects only have microsecond precision (6 digits). Any additional precision will be truncated.

Time Zone Information

Time zone information may be provided in one of the following formats:

Format	Example	Supported
Z	Z	✅
z	z	✅
±hh	+11	✅
±hhmm	+1130	✅
±hh:mm	+11:30	✅

While the ISO 8601 specification allows the use of MINUS SIGN (U+2212) in the time zone separator, ciso8601 only supports the use of the HYPHEN-MINUS (U+002D) character.

Consistent with RFC 3339, ciso860 also allows a lower-case z to be used instead of a Z.

Strict RFC 3339 Parsing

ciso8601 parses ISO 8601 datetimes, which can be thought of as a superset of RFC 3339 (roughly). In cases where you might want strict RFC 3339 parsing, ciso8601 offers a parse_rfc3339 method, which behaves in a similar manner to parse_datetime:

parse_rfc3339(dt: String): datetime is a function that takes a string and either:

• Returns a properly parsed Python datetime, if and only if the entire string conforms to RFC 3339.
• Raises a ValueError with a description of the reason why the string doesn't conform to RFC 3339.

Ignoring Timezone Information While Parsing

It takes more time to parse timestamps with time zone information, especially if they're not in UTC. However, there are times when you don't care about time zone information, and wish to produce naive datetimes instead. For example, if you are certain that your program will only parse timestamps from a single time zone, you might want to strip the time zone information and only output naive datetimes.

In these limited cases, there is a second function provided. parse_datetime_as_naive will ignore any time zone information it finds and, as a result, is faster for timestamps containing time zone information.

In [1]: import ciso8601

In [2]: ciso8601.parse_datetime_as_naive('2014-12-05T12:30:45.123456-05:30')
Out[2]: datetime.datetime(2014, 12, 5, 12, 30, 45, 123456)

NOTE: parse_datetime_as_naive is only useful in the case where your timestamps have time zone information, but you want to ignore it. This is somewhat unusual. If your timestamps don't have time zone information (i.e. are naive), simply use parse_datetime. It is just as fast.