1 files changed, 114 insertions, 0 deletions
diff --git a/python/skytools/timeutil.py b/python/skytools/timeutil.py
new file mode 100644
index 00000000..b6728bf2
--- /dev/null
+++ b/python/skytools/timeutil.py
@@ -0,0 +1,114 @@
+
+"""Module for parsing ISO 8601 format timestamps.
+
+Only fixed offset timezones are supported.
+
+http://en.wikipedia.org/wiki/ISO_8601
+"""
+
+import re
+
+from datetime import datetime, timedelta, tzinfo
+
+"""
+TODO:
+- support more combinations from ISO 8601 (only reasonable ones)
+- cache TZ objects
+- make it faster?
+"""
+
+__all__ = ['parse_iso_timestamp', 'FixedOffsetTimezone']
+
+class FixedOffsetTimezone(tzinfo):
+    """Fixed offset in minutes east from UTC."""
+    __slots__ = ('__offset', '__name')
+
+    def __init__(self, offset):
+        self.__offset = timedelta(minutes = offset)
+
+        # numeric tz name
+        h, m = divmod(abs(offset), 60)
+        if offset < 0:
+            h = -h
+        if m:
+            self.__name = "%+03d:%02d" % (h,m)
+        else:
+            self.__name = "%+03d" % h
+
+    def utcoffset(self, dt):
+        return self.__offset
+
+    def tzname(self, dt):
+        return self.__name
+
+    def dst(self, dt):
+        return ZERO
+
+ZERO = timedelta(0)
+
+_iso_regex = r"""
+    \s*
+    (?P<year> \d\d\d\d) [-] (?P<month> \d\d) [-] (?P<day> \d\d) [ T]
+    (?P<hour> \d\d) [:] (?P<min> \d\d)
+    (?: [:] (?P<sec> \d\d ) (?: [.,] (?P<ss> \d+))? )?
+    (?: \s*  (?P<tzsign> [-+]) (?P<tzhr> \d\d) (?: [:]? (?P<tzmin> \d\d))? )?
+    \s* $
+    """
+_iso_rc = None
+
+def parse_iso_timestamp(s, default_tz = None):
+    """Parse ISO timestamp to datetime object.
+    
+    YYYY-MM-DD[ T]HH:MM[:SS[.ss]][-+HH[:MM]]
+
+    Assumes that second fractions are zero-trimmed from the end,
+    so '.15' means 150000 microseconds.
+
+    If the timezone offset is not present, use default_tz as tzinfo.
+    By default its None, meaning the datetime object will be without tz.
+
+    >>> str(parse_iso_timestamp('2005-06-01 15:00'))
+    '2005-06-01 15:00:00'
+    >>> str(parse_iso_timestamp(' 2005-06-01T15:00 +02 '))
+    '2005-06-01 15:00:00+02:00'
+    >>> str(parse_iso_timestamp('2005-06-01 15:00:33+02:00'))
+    '2005-06-01 15:00:33+02:00'
+    >>> d = parse_iso_timestamp('2005-06-01 15:00:59.33 +02')
+    >>> d.strftime("%z %Z")
+    '+0200 +02'
+    >>> str(parse_iso_timestamp(str(d)))
+    '2005-06-01 15:00:59.330000+02:00'
+    >>> parse_iso_timestamp('2005-06-01 15:00-0530').strftime('%Y-%m-%d %H:%M %z %Z')
+    '2005-06-01 15:00 -0530 -05:30'
+    """
+
+    global _iso_rc
+    if _iso_rc is None:
+        _iso_rc = re.compile(_iso_regex, re.X)
+
+    m = _iso_rc.match(s)
+    if not m:
+        raise ValueError('Date not in ISO format: %s' % repr(s))
+
+    tz = default_tz
+    if m.group('tzsign'):
+        tzofs = int(m.group('tzhr')) * 60
+        if m.group('tzmin'):
+            tzofs += int(m.group('tzmin'))
+        if m.group('tzsign') == '-':
+            tzofs = -tzofs
+        tz = FixedOffsetTimezone(tzofs)
+
+    return datetime(int(m.group('year')),
+                int(m.group('month')),
+                int(m.group('day')),
+                int(m.group('hour')),
+                int(m.group('min')),
+                m.group('sec') and int(m.group('sec')) or 0,
+                m.group('ss') and int(m.group('ss').ljust(6, '0')) or 0,
+                tz)
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
+