ENH: Adding date parser to get_armfiles. (#449)

* ENH: Adding date parser to get_armfiles.

* FIX: Forgot datetime import.

* ENH: Adding output format and return datetime obj parameters.
Also moving function to datetimeutils.

* TST: Adding unittests for date_parser.

* FIX: Forgot full import.

act/discovery/get_armfiles.py

@@ -13,6 +13,8 @@
 except ImportError:
     from urllib import urlopen
 
+from act.utils import date_parser
+
 
 def download_data(username, token, datastream, startdate, enddate, time=None, output=None):
     """
@@ -28,9 +30,11 @@ def download_data(username, token, datastream, startdate, enddate, time=None, ou
     datastream : str
         The name of the datastream to acquire.
     startdate : str
-        The start date of the data to acquire. Format is YYYY-MM-DD.
+        The start date of the data to acquire. Formats accepted are
+        YYYY-MM-DD, DD.MM.YYYY, DD/MM/YYYY, YYYYMMDD or YYYY/MM/DD.
     enddate : str
-        The end date of the data to acquire. Format is YYYY-MM-DD.
+        The end date of the data to acquire. Formats accepted are
+        YYYY-MM-DD, DD.MM.YYYY, DD/MM/YYYY, YYYYMMDD or YYYY/MM/DD.
     time: str or None
         The specific time. Format is HHMMSS. Set to None to download all files
         in the given date interval.
@@ -88,8 +92,10 @@ def download_data(username, token, datastream, startdate, enddate, time=None, ou
     # start and end strings for query_url are constructed
     # if the arguments were provided
     if startdate:
+        start = date_parser(startdate, output_format='%Y-%m-%d')
         start = f'&start={startdate}'
     if enddate:
+        end = date_parser(enddate, output_format='%Y-%m-%d')
         end = f'&end={enddate}'
     # build the url to query the web service using the arguments provided
     query_url = (

act/tests/test_utils.py

@@ -599,3 +599,19 @@ def test_height_adjusted_pressure():
             pressure=obj[press_var_name].values,
             press_var_units=None,
         )
+
+
+def test_date_parser():
+    datestring = '20111001'
+    output_format = '%Y/%m/%d'
+
+    test_string = act.utils.date_parser(
+        datestring, output_format, return_datetime=False)
+    assert test_string == '2011/10/01'
+
+    test_datetime = act.utils.date_parser(
+        datestring, output_format, return_datetime=True)
+    assert test_datetime == datetime(2011, 10, 1)
+
+    pytest.raises(
+        ValueError, act.utils.date_parser, '0511')

act/utils/__init__.py

@@ -20,6 +20,7 @@
     determine_time_delta,
     numpy_to_arm_date,
     reduce_time_ranges,
+    date_parser,
 )
 from .geo_utils import add_solar_variable, destination_azimuth_distance
 from .inst_utils import decode_present_weather

act/utils/datetime_utils.py

@@ -109,8 +109,8 @@ def reduce_time_ranges(time, time_delta=60, broken_barh=False):
 
 def determine_time_delta(time, default=60):
     """
-    Returns the most likely time step in seconds by analyzing the difference in
-    time steps.
+    Returns the most likely time step in seconds by analyzing the difference
+    in time steps.
 
     Parameters
     ----------
@@ -140,17 +140,19 @@ def determine_time_delta(time, default=60):
 
 def datetime64_to_datetime(time):
     """
-    Given a numpy datetime64 array time series, return datetime (y, m, d, h, m, s)
+    Given a numpy datetime64 array time series, return datetime
+    (y, m, d, h, m, s)
 
     Parameters
     ----------
-    time: numpy datetime64 array, list of numpy datetime64 values or scalar numpy datetime64
-        The numpy array of date time values.
+    time : numpy datetime64 array, list of numpy datetime64 values or
+        scalar numpy datetime64. The numpy array of date time values.
 
     Returns
     -------
-    datetime: list
+    datetime : list
         Returns a list of datetimes (y, m, d, h, m, s) from a time series.
+        YYYY-MM-DD, DD.MM.YYYY, DD/MM/YYYY or YYYYMMDD.
 
     """
     if isinstance(time, (tuple, list)):
@@ -164,3 +166,44 @@ def datetime64_to_datetime(time):
         for tm in time
     ]
     return datetime_array
+
+
+def date_parser(date_string, output_format='%Y%m%d',
+                return_datetime=False):
+    """ Converts one datetime string to another or to
+    a datetime object.
+
+    Parameters
+    ----------
+    date_string : str
+        datetime string to be parsed. Accepted formats are
+        YYYY-MM-DD, DD.MM.YYYY, DD/MM/YYYY or YYYYMMDD.
+    output_format : str
+        Format for datetime.strftime to output datetime string.
+    return_datetime : bool
+        If true, returns str as a datetime object.
+        Default is False.
+
+    returns
+    -------
+    datetime_str : str
+        A valid datetime string.
+    datetime_obj : datetime.datetime
+        A datetime object.
+
+    """
+    date_fmts = ['%Y-%m-%d', '%d.%m.%Y',
+                 '%d/%m/%Y', '%Y%m%d', '%Y/%m/%d']
+    for fmt in date_fmts:
+        try:
+            datetime_obj = dt.datetime.strptime(date_string, fmt)
+            if return_datetime:
+                return datetime_obj
+            else:
+                return datetime_obj.strftime(output_format)
+        except ValueError:
+            pass
+    fmt_strings = ', '.join(date_fmts)
+    raise ValueError(
+        'Invalid Date format, please use one of these formats '
+        + fmt_strings)