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datetimeutil.py

# (c) 2005 Clark C. Evans and contributors
# This module is part of the Python Paste Project and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
# Some of this code was funded by: http://prometheusresearch.com
"""
Date, Time, and Timespan Parsing Utilities

This module contains parsing support to create "human friendly"
``datetime`` object parsing.  The explicit goal of these routines is
to provide a multi-format date/time support not unlike that found in
Microsoft Excel.  In most approaches, the input is very "strict" to
prevent errors -- however, this approach is much more liberal since we
are assuming the user-interface is parroting back the normalized value
and thus the user has immediate feedback if the data is not typed in
correctly.

  ``parse_date`` and ``normalize_date``

     These functions take a value like '9 jan 2007' and returns either an
     ``date`` object, or an ISO 8601 formatted date value such
     as '2007-01-09'.  There is an option to provide an Oracle database
     style output as well, ``09 JAN 2007``, but this is not the default.

     This module always treats '/' delimiters as using US date order
     (since the author's clients are US based), hence '1/9/2007' is
     January 9th.  Since this module treats the '-' as following
     European order this supports both modes of data-entry; together
     with immediate parroting back the result to the screen, the author
     has found this approach to work well in pratice.

  ``parse_time`` and ``normalize_time``

     These functions take a value like '1 pm' and returns either an
     ``time`` object, or an ISO 8601 formatted 24h clock time
     such as '13:00'.  There is an option to provide for US style time
     values, '1:00 PM', however this is not the default.

  ``parse_datetime`` and ``normalize_datetime``

     These functions take a value like '9 jan 2007 at 1 pm' and returns
     either an ``datetime`` object, or an ISO 8601 formatted
     return (without the T) such as '2007-01-09 13:00'. There is an
     option to provide for Oracle / US style, '09 JAN 2007 @ 1:00 PM',
     however this is not the default.

  ``parse_delta`` and ``normalize_delta``

     These functions take a value like '1h 15m' and returns either an
     ``timedelta`` object, or an 2-decimal fixed-point
     numerical value in hours, such as '1.25'.  The rationale is to
     support meeting or time-billing lengths, not to be an accurate
     representation in mili-seconds.  As such not all valid
     ``timedelta`` values will have a normalized representation.

"""
from datetime import timedelta, time, date
from time import localtime
import string

__all__ = ['parse_timedelta', 'normalize_timedelta',
           'parse_time', 'normalize_time',
           'parse_date', 'normalize_date']

def _number(val):
    try:
        return string.atoi(val)
    except:
        return None

#
# timedelta
#
def parse_timedelta(val):
    """
    returns a ``timedelta`` object, or None
    """
    if not val:
        return None
    val = string.lower(val)
    if "." in val:
        val = float(val)
        return timedelta(hours=int(val), minutes=60*(val % 1.0))
    fHour = ("h" in val or ":" in val)
    fMin  = ("m" in val or ":" in val)
    fFraction = "." in val
    for noise in "minu:teshour()":
        val = string.replace(val, noise, ' ')
    val = string.strip(val)
    val = string.split(val)
    hr = 0.0
    mi = 0
    val.reverse()
    if fHour:
        hr = int(val.pop())
    if fMin:
        mi = int(val.pop())
    if len(val) > 0 and not hr:
        hr = int(val.pop())
    return timedelta(hours=hr, minutes=mi)

def normalize_timedelta(val):
    """
    produces a normalized string value of the timedelta

    This module returns a normalized time span value consisting of the
    number of hours in fractional form. For example '1h 15min' is
    formatted as 01.25.
    """
    if type(val) == str:
        val = parse_timedelta(val)
    if not val:
        return ''
    hr = val.seconds/3600
    mn = (val.seconds % 3600)/60
    return "%d.%02d" % (hr, mn * 100/60)

#
# time
#
def parse_time(val):
    if not val:
        return None
    hr = mi = 0
    val = string.lower(val)
    amflag = (-1 != string.find(val, 'a'))  # set if AM is found
    pmflag = (-1 != string.find(val, 'p'))  # set if PM is found
    for noise in ":amp.":
        val = string.replace(val, noise, ' ')
    val = string.split(val)
    if len(val) > 1:
        hr = int(val[0])
        mi = int(val[1])
    else:
        val = val[0]
        if len(val) < 1:
            pass
        elif 'now' == val:
            tm = localtime()
            hr = tm[3]
            mi = tm[4]
        elif 'noon' == val:
            hr = 12
        elif len(val) < 3:
            hr = int(val)
            if not amflag and not pmflag and hr < 7:
                hr += 12
        elif len(val) < 5:
            hr = int(val[:-2])
            mi = int(val[-2:])
        else:
            hr = int(val[:1])
    if amflag and hr >= 12:
        hr = hr - 12
    if pmflag and hr < 12:
        hr = hr + 12
    return time(hr, mi)

def normalize_time(value, ampm):
    if not value:
        return ''
    if type(value) == str:
        value = parse_time(value)
    if not ampm:
        return "%02d:%02d" % (value.hour, value.minute)
    hr = value.hour
    am = "AM"
    if hr < 1 or hr > 23:
        hr = 12
    elif hr >= 12:
        am = "PM"
        if hr > 12:
            hr = hr - 12
    return "%02d:%02d %s" % (hr, value.minute, am)

#
# Date Processing
#

_one_day = timedelta(days=1)

_str2num = {'jan':1, 'feb':2, 'mar':3, 'apr':4,  'may':5, 'jun':6,
            'jul':7, 'aug':8, 'sep':9, 'oct':10, 'nov':11, 'dec':12 }

def _month(val):
    for (key, mon) in _str2num.items():
        if key in val:
            return mon
    raise TypeError("unknown month '%s'" % val)

_days_in_month = {1: 31, 2: 28, 3: 31, 4: 30, 5: 31, 6: 30,
                  7: 31, 8: 31, 9: 30, 10: 31, 11: 30, 12: 31,
                  }
_num2str = {1: 'Jan', 2: 'Feb', 3: 'Mar', 4: 'Apr', 5: 'May', 6: 'Jun',
            7: 'Jul', 8: 'Aug', 9: 'Sep', 10: 'Oct', 11: 'Nov', 12: 'Dec',
            }
_wkdy = ("mon", "tue", "wed", "thu", "fri", "sat", "sun")

def parse_date(val):
    if not(val):
        return None
    val = string.lower(val)
    now = None

    # optimized check for YYYY-MM-DD
    strict = val.split("-")
    if len(strict) == 3:
        (y, m, d) = strict
        if "+" in d:
            d = d.split("+")[0]
        if " " in d:
            d = d.split(" ")[0]
        try:
            now = date(int(y), int(m), int(d))
            val = "xxx" + val[10:]
        except ValueError:
            pass

    # allow for 'now', 'mon', 'tue', etc.
    if not now:
        chk = val[:3]
        if chk in ('now','tod'):
            now = date.today()
        elif chk in _wkdy:
            now = date.today()
            idx = list(_wkdy).index(chk) + 1
            while now.isoweekday() != idx:
                now += _one_day

    # allow dates to be modified via + or - /w number of days, so
    # that now+3 is three days from now
    if now:
        tail = val[3:].strip()
        tail = tail.replace("+"," +").replace("-"," -")
        for item in tail.split():
            try:
                days = int(item)
            except ValueError:
                pass
            else:
                now += timedelta(days=days)
        return now

    # ok, standard parsing
    yr = mo = dy = None
    for noise in ('/', '-', ',', '*'):
        val = string.replace(val, noise, ' ')
    for noise in _wkdy:
        val = string.replace(val, noise, ' ')
    out = []
    last = False
    ldig = False
    for ch in val:
        if ch.isdigit():
            if last and not ldig:
               out.append(' ')
            last = ldig = True
        else:
            if ldig:
                out.append(' ')
                ldig = False
            last = True
        out.append(ch)
    val = string.split("".join(out))
    if 3 == len(val):
        a = _number(val[0])
        b = _number(val[1])
        c = _number(val[2])
        if len(val[0]) == 4:
            yr = a
            if b:  # 1999 6 23
                mo = b
                dy = c
            else:  # 1999 Jun 23
                mo = _month(val[1])
                dy = c
        elif a > 0:
            yr = c
            if len(val[2]) < 4:
                raise TypeError("four digit year required")
            if b: # 6 23 1999
                dy = b
                mo = a
            else: # 23 Jun 1999
                dy = a
                mo = _month(val[1])
        else: # Jun 23, 2000
            dy = b
            yr = c
            if len(val[2]) < 4:
                raise TypeError("four digit year required")
            mo = _month(val[0])
    elif 2 == len(val):
        a = _number(val[0])
        b = _number(val[1])
        if a > 999:
            yr = a
            dy = 1
            if b > 0: # 1999 6
                mo = b
            else: # 1999 Jun
                mo = _month(val[1])
        elif a > 0:
            if b > 999: # 6 1999
                mo = a
                yr = b
                dy = 1
            elif b > 0: # 6 23
                mo = a
                dy = b
            else: # 23 Jun
                dy = a
                mo = _month(val[1])
        else:
            if b > 999: # Jun 2001
                yr = b
                dy = 1
            else:  # Jun 23
                dy = b
            mo = _month(val[0])
    elif 1 == len(val):
        val = val[0]
        if not val.isdigit():
            mo = _month(val)
            if mo is not None:
                dy = 1
        else:
            v = _number(val)
            val = str(v)
            if 8 == len(val): # 20010623
                yr = _number(val[:4])
                mo = _number(val[4:6])
                dy = _number(val[6:])
            elif len(val) in (3,4):
                if v > 1300: # 2004
                    yr = v
                    mo = 1
                    dy = 1
                else:        # 1202
                    mo = _number(val[:-2])
                    dy = _number(val[-2:])
            elif v < 32:
                dy = v
            else:
                raise TypeError("four digit year required")
    tm = localtime()
    if mo is None:
        mo = tm[1]
    if dy is None:
        dy = tm[2]
    if yr is None:
        yr = tm[0]
    return date(yr, mo, dy)

def normalize_date(val, iso8601=True):
    if not val:
        return ''
    if type(val) == str:
        val = parse_date(val)
    if iso8601:
        return "%4d-%02d-%02d" % (val.year, val.month, val.day)
    return "%02d %s %4d" % (val.day, _num2str[val.month], val.year)

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