Update metar.py default year, month to keyword-only and None

src/metpy/io/metar.py

@@ -61,7 +61,7 @@
 
 
 @exporter.export
-def parse_metar_to_dataframe(metar_text, year=datetime.now().year, month=datetime.now().month):
+def parse_metar_to_dataframe(metar_text, *, year=None, month=None):
     """Parse a single METAR report into a Pandas DataFrame.
 
     Takes a METAR string in a text form, and creates a `pandas.DataFrame` including the
@@ -76,9 +76,9 @@ def parse_metar_to_dataframe(metar_text, year=datetime.now().year, month=datetim
     metar_text : str
         The METAR report
     year : int, optional
-        Year in which observation was taken, defaults to the current year
+        Year in which observation was taken, defaults to current year. Keyword-only argument.
     month : int, optional
-        Month in which observation was taken, defaults to the current month
+        Month in which observation was taken, defaults to current month. Keyword-only argument.
 
     Returns
     -------
@@ -116,6 +116,12 @@ def parse_metar_to_dataframe(metar_text, year=datetime.now().year, month=datetim
     and altimeter value, float
 
     """
+    # Defaults year and/or month to present reported date if not provided
+    if year is None or month is None:
+        now = datetime.now()
+        year = now.year if year is None else year
+        month = now.month if month is None else month
+
     # Use the named tuple parsing function to separate metar
     # Utilizes the station dictionary which contains elevation, latitude, and longitude
     metar_vars = parse_metar_to_named_tuple(metar_text, station_info, year, month)
@@ -176,8 +182,7 @@ def parse_metar_to_dataframe(metar_text, year=datetime.now().year, month=datetim
     return df
 
 
-def parse_metar_to_named_tuple(metar_text, station_metadata, year=datetime.now().year,
-                               month=datetime.now().month):
+def parse_metar_to_named_tuple(metar_text, station_metadata, year, month):
     """Parse a METAR report in text form into a list of named tuples.
 
     Parameters
@@ -186,10 +191,15 @@ def parse_metar_to_named_tuple(metar_text, station_metadata, year=datetime.now()
         The METAR report
     station_metadata : dict
         Mapping of station identifiers to station metadata
+    year : int
+        Reported year of observation for constructing 'date_time'
+    month : int
+        Reported month of observation for constructing 'date_time'
 
     Returns
     -------
-    `pandas.DataFrame`
+    metar : namedtuple
+        Named tuple of parsed METAR fields
 
     Notes
     -----
@@ -424,7 +434,7 @@ def parse_metar_to_named_tuple(metar_text, station_metadata, year=datetime.now()
 
 
 @exporter.export
-def parse_metar_file(filename, year=datetime.now().year, month=datetime.now().month):
+def parse_metar_file(filename, *, year=None, month=None):
     """Parse a text file containing multiple METAR reports and/or text products.
 
     Parameters
@@ -433,9 +443,9 @@ def parse_metar_file(filename, year=datetime.now().year, month=datetime.now().mo
         If str, the name of the file to be opened. If `filename` is a file-like object,
         this will be read from directly.
     year : int, optional
-        Year in which observation was taken, defaults to the current year
+        Year in which observation was taken, defaults to current year. Keyword-only argument.
     month : int, optional
-        Month in which observation was taken, defaults to the current month
+        Month in which observation was taken, defaults to current month. Keyword-only argument.
 
     Returns
     -------
@@ -473,6 +483,12 @@ def parse_metar_file(filename, year=datetime.now().year, month=datetime.now().mo
     and altimeter value, float
 
     """
+    # Defaults year and/or month to present reported date if not provided
+    if year is None or month is None:
+        now = datetime.now()
+        year = now.year if year is None else year
+        month = now.month if month is None else month
+
     # Function to merge METARs
     def merge(x, key='     '):
         tmp = []

tests/io/test_metar.py

@@ -6,6 +6,7 @@
 
 import numpy as np
 from numpy.testing import assert_almost_equal, assert_equal
+import pytest
 
 from metpy.cbook import get_test_data
 from metpy.io import parse_metar_file, parse_metar_to_dataframe
@@ -98,6 +99,14 @@ def test_date_time_given():
     assert df.northward_wind.values == 0
 
 
+def test_parse_metar_df_positional_datetime_failure():
+    """Test that positional year, month arguments fail for parse_metar_to_dataframe."""
+    # pylint: disable=too-many-function-args
+    with pytest.raises(TypeError, match='takes 1 positional argument but 3 were given'):
+        parse_metar_to_dataframe('K6B0 261200Z AUTO 00000KT 10SM CLR 20/M17'
+                                 'A3002 RMK AO2 T01990165=', 2019, 6)
+
+
 def test_named_tuple_test1():
     """Test the named tuple parsing function."""
     df = parse_metar_to_dataframe('KDEN 012153Z 09010KT 10SM FEW060 BKN110 BKN220 27/13 '
@@ -118,6 +127,14 @@ def test_parse_file():
     assert test.air_pressure_at_sea_level.values == 1016.76
 
 
+def test_parse_file_positional_datetime_failure():
+    """Test that positional year, month arguments fail for parse_metar_file."""
+    # pylint: disable=too-many-function-args
+    input_file = get_test_data('metar_20190701_1200.txt', as_file_obj=False)
+    with pytest.raises(TypeError, match='takes 1 positional argument but 3 were given'):
+        parse_metar_file(input_file, 2016, 12)
+
+
 def test_parse_file_bad_encoding():
     """Test the parser on an entire file that has at least one bad utf-8 encoding."""
     input_file = get_test_data('2020010600_sao.wmo', as_file_obj=False)