datetime parsing for python 3.7 thru 3.12; fix deprecation warning

Author: Kyle A Logue

README.md

@@ -100,7 +100,7 @@ import datetime as dt
 import numpy as np
 import sigmf
 from sigmf import SigMFFile
-from sigmf.utils import get_data_type_str
+from sigmf.utils import get_data_type_str, get_sigmf_iso8601_datetime_now
 
 # suppose we have an complex timeseries signal
 data = np.zeros(1024, dtype=np.complex64)
@@ -122,7 +122,7 @@ meta = SigMFFile(
 # create a capture key at time index 0
 meta.add_capture(0, metadata={
     SigMFFile.FREQUENCY_KEY: 915000000,
-    SigMFFile.DATETIME_KEY: dt.datetime.utcnow().isoformat()+'Z',
+    SigMFFile.DATETIME_KEY: get_sigmf_iso8601_datetime_now(),
 })
 
 # add an annotation at sample 100 with length 200 & 10 KHz width

sigmf/apps/convert_wav.py

@@ -7,24 +7,29 @@
 """converter for wav containers"""
 
 import argparse
-import datetime
 import getpass
 import logging
 import os
 import pathlib
 import tempfile
+from typing import Optional
 
 from scipy.io import wavfile
 
 from .. import SigMFFile, __specification__
 from .. import __version__ as toolversion
 from .. import archive
-from ..utils import get_data_type_str
+from ..utils import get_data_type_str, get_sigmf_iso8601_datetime_now
 
 log = logging.getLogger()
 
 
-def convert_wav(input_wav_filename, archive_filename=None, start_datetime=None, author=None):
+def convert_wav(
+    input_wav_filename: str,
+    archive_filename: Optional[str],
+    start_datetime: Optional[str] = None,
+    author: Optional[str] = None,
+):
     """
     read a .wav and write a .sigmf archive
     """
@@ -43,12 +48,12 @@ def convert_wav(input_wav_filename, archive_filename=None, start_datetime=None,
     }
 
     if start_datetime is None:
-        mtime = datetime.datetime.fromtimestamp(input_path.stat().st_mtime)
-        start_datetime = mtime.isoformat() + "Z"
+        start_datetime = get_sigmf_iso8601_datetime_now()
 
-    capture_info = {SigMFFile.START_INDEX_KEY: 0}
-    if start_datetime is not None:
-        capture_info[SigMFFile.DATETIME_KEY] = start_datetime
+    capture_info = {
+        SigMFFile.START_INDEX_KEY: 0,
+        SigMFFile.DATETIME_KEY: start_datetime,
+    }
 
     tmpdir = tempfile.mkdtemp()
     sigmf_data_filename = input_stem + archive.SIGMF_DATASET_EXT
@@ -71,8 +76,8 @@ def main():
     parser = argparse.ArgumentParser(description="Convert .wav to .sigmf container.")
     parser.add_argument("input", type=str, help="Wavfile path")
     parser.add_argument("--author", type=str, default=None, help=f"set {SigMFFile.AUTHOR_KEY} metadata")
-    parser.add_argument('-v', '--verbose', action='count', default=0)
-    parser.add_argument('--version', action='version', version=f'%(prog)s v{toolversion}')
+    parser.add_argument("-v", "--verbose", action="count", default=0)
+    parser.add_argument("--version", action="version", version=f"%(prog)s v{toolversion}")
     args = parser.parse_args()
 
     level_lut = {

sigmf/utils.py

@@ -9,7 +9,7 @@
 import re
 import sys
 from copy import deepcopy
-from datetime import datetime
+from datetime import datetime, timezone
 
 import numpy as np
 
@@ -19,31 +19,34 @@
 
 
 def get_sigmf_iso8601_datetime_now() -> str:
-    """Get current UTC time as iso8601 string"""
-    return datetime.isoformat(datetime.utcnow()) + "Z"
+    """Get current UTC time as iso8601 string."""
+    return datetime.now(timezone.utc).strftime(SIGMF_DATETIME_ISO8601_FMT)
 
 
-def parse_iso8601_datetime(datestr: str) -> datetime:
+def parse_iso8601_datetime(string: str) -> datetime:
     """
-    Parse an iso8601 string as a datetime
+    Parse an iso8601 string as a datetime struct.
+    Input string (indicated by final Z) is in UTC tz.
 
     Example
     -------
     >>> parse_iso8601_datetime("1955-11-05T06:15:00Z")
-    datetime.datetime(1955, 11, 5, 6, 15)
+    datetime.datetime(1955, 11, 5, 6, 15, tzinfo=datetime.timezone.utc)
     """
-    # provided string exceeds max precision -> truncate to µs
-    match = re.match(r"^(?P<dt>.*)(?P<frac>\.[0-9]{7,})Z$", datestr)
+    match = re.match(r"^(?P<dt>.*)(?P<frac>\.[0-9]{7,})Z$", string)
     if match:
-        md = match.groupdict()
-        length = min(7, len(md["frac"]))
-        datestr = ''.join([md["dt"], md["frac"][:length], "Z"])
-
-    try:
-        timestamp = datetime.strptime(datestr, '%Y-%m-%dT%H:%M:%S.%fZ')
-    except ValueError:
-        timestamp = datetime.strptime(datestr, '%Y-%m-%dT%H:%M:%SZ')
-    return timestamp
+        # string exceeds max precision allowed by strptime -> truncate to µs
+        groups = match.groupdict()
+        length = min(7, len(groups["frac"]))
+        string = "".join([groups["dt"], groups["frac"][:length], "Z"])
+
+    if "." in string:
+        # parse float seconds
+        format_str = SIGMF_DATETIME_ISO8601_FMT
+    else:
+        # parse whole seconds
+        format_str = SIGMF_DATETIME_ISO8601_FMT.replace(".%f", "")
+    return datetime.strptime(string, format_str).replace(tzinfo=timezone.utc)
 
 
 def dict_merge(a_dict: dict, b_dict: dict) -> dict:
@@ -83,11 +86,10 @@ def get_endian_str(ray: np.ndarray) -> str:
 
     if atype.byteorder == "<":
         return "_le"
-    elif atype.byteorder == ">":
+    if atype.byteorder == ">":
         return "_be"
-    else:
-        # endianness is then either '=' (native) or '|' (doesn't matter)
-        return "_le" if sys.byteorder == "little" else "_be"
+    # endianness is then either '=' (native) or '|' (doesn't matter)
+    return "_le" if sys.byteorder == "little" else "_be"
 
 
 def get_data_type_str(ray: np.ndarray) -> str:

tests/test_utils.py

@@ -6,22 +6,30 @@
 
 """Tests for Utilities"""
 
-from datetime import datetime
+from datetime import datetime, timezone
 
 import pytest
 
 from sigmf import utils
 
 
-@pytest.mark.parametrize("ts, expected", [
-    ("1955-07-04T05:15:00Z",                datetime(year=1955, month=7,  day=4, hour=5,  minute=15, second=00, microsecond=0)),
-    ("2956-08-05T06:15:12Z",                datetime(year=2956, month=8,  day=5, hour=6,  minute=15, second=12, microsecond=0)),
-    ("3957-09-06T07:15:12.345Z",            datetime(year=3957, month=9,  day=6, hour=7,  minute=15, second=12, microsecond=345000)),
-    ("4958-10-07T08:15:12.0345Z",           datetime(year=4958, month=10, day=7, hour=8,  minute=15, second=12, microsecond=34500)),
-    ("5959-11-08T09:15:12.000000Z",         datetime(year=5959, month=11, day=8, hour=9,  minute=15, second=12, microsecond=0)),
-    ("6960-12-09T10:15:12.123456789123Z",   datetime(year=6960, month=12, day=9, hour=10, minute=15, second=12, microsecond=123456)),
+@pytest.mark.parametrize("time_str, expected", [
+    ("1955-07-04T05:15:00Z",                datetime(year=1955, month=7,  day=4, hour=5,  minute=15, second=00, microsecond=0, tzinfo=timezone.utc)),
+    ("2956-08-05T06:15:12Z",                datetime(year=2956, month=8,  day=5, hour=6,  minute=15, second=12, microsecond=0, tzinfo=timezone.utc)),
+    ("3957-09-06T07:15:12.345Z",            datetime(year=3957, month=9,  day=6, hour=7,  minute=15, second=12, microsecond=345000, tzinfo=timezone.utc)),
+    ("4958-10-07T08:15:12.0345Z",           datetime(year=4958, month=10, day=7, hour=8,  minute=15, second=12, microsecond=34500, tzinfo=timezone.utc)),
+    ("5959-11-08T09:15:12.000000Z",         datetime(year=5959, month=11, day=8, hour=9,  minute=15, second=12, microsecond=0, tzinfo=timezone.utc)),
+    ("6960-12-09T10:15:12.123456789123Z",   datetime(year=6960, month=12, day=9, hour=10, minute=15, second=12, microsecond=123456, tzinfo=timezone.utc)),
 
 ])
-def test_parse_simple_iso8601(ts, expected):
-    dt = utils.parse_iso8601_datetime(ts)
-    assert dt == expected
+def test_parse_simple_iso8601(time_str: str, expected: datetime) -> None:
+    """Ensure various times are represented as expected"""
+    date_struct = utils.parse_iso8601_datetime(time_str)
+    assert date_struct == expected
+
+
+def test_roundtrip_datetime() -> None:
+    """New string -> struct -> string is ok"""
+    now_str = utils.get_sigmf_iso8601_datetime_now()
+    now_struct = utils.parse_iso8601_datetime(now_str)
+    assert now_str == now_struct.strftime(utils.SIGMF_DATETIME_ISO8601_FMT)