fix datetime bug & add typing

* start to add typing to module
* fix bug so that when converting sigmf datetime to isoformat
  will now allow seconds with or without decimal

sigmf/utils.py

@@ -4,7 +4,7 @@
 #
 # SPDX-License-Identifier: LGPL-3.0-or-later
 
-'''Utilities'''
+"""Utilities"""
 
 from copy import deepcopy
 from datetime import datetime
@@ -16,17 +16,37 @@
 SIGMF_DATETIME_ISO8601_FMT = "%Y-%m-%dT%H:%M:%S.%fZ"
 
 
-def get_sigmf_iso8601_datetime_now():
-    return datetime.isoformat(datetime.utcnow()) + 'Z'
+def get_sigmf_iso8601_datetime_now() -> str:
+    """Get current UTC time as iso8601 string"""
+    return datetime.isoformat(datetime.utcnow()) + "Z"
 
 
-def parse_iso8601_datetime(datestr):
-    return datetime.strptime(datestr, SIGMF_DATETIME_ISO8601_FMT)
+def parse_iso8601_datetime(datestr: str) -> datetime:
+    """
+    Parse an iso8601 string as a datetime
+
+    Example
+    -------
+    >>> parse_iso8601_datetime("1955-11-05T06:15:00Z")
+    datetime.datetime(1955, 11, 5, 6, 15)
+    """
+    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
 
 
-def dict_merge(a_dict, b_dict):
+def dict_merge(a_dict: dict, b_dict: dict) -> dict:
     """
-    Recursively merge b_dict into a_dict. b_dict[key] will overwrite a_dict[key] if it exists.
+    Recursively merge `b_dict` into `a_dict`.
+    `b_dict[key]` will overwrite `a_dict[key]` if it exists.
+
+    Example
+    -------
+    >>> a, b = {0:0, 1:2}, {1:3, 2:4}
+    >>> dict_merge(a, b)
+    {0: 0, 1: 3, 2: 4}
     """
     if not isinstance(b_dict, dict):
         return b_dict
@@ -39,50 +59,52 @@ def dict_merge(a_dict, b_dict):
     return result
 
 
-def get_schema_path(module_path):
+def get_schema_path(module_path: str) -> str:
     """
+    TODO: Allow getting different schemas for specific SigMF versions
     """
     return module_path
 
 
-def get_endian_str(ray):
+def get_endian_str(ray: np.ndarray) -> str:
+    """Return SigMF compatible endianness string for a numpy array"""
     if not isinstance(ray, np.ndarray):
-        raise error.SigMFError('Argument must be a numpy array')
+        raise error.SigMFError("Argument must be a numpy array")
     atype = ray.dtype
 
-    if atype.byteorder == '<':
-        return '_le'
-    elif atype.byteorder == '>':
-        return '_be'
+    if atype.byteorder == "<":
+        return "_le"
+    elif atype.byteorder == ">":
+        return "_be"
     else:
-        # endianness must be 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):
+def get_data_type_str(ray: np.ndarray) -> str:
     """
     Return the SigMF datatype string for the datatype of numpy array `ray`.
 
     NOTE: this function only supports native numpy types so interleaved complex
     integer types are not supported.
     """
     if not isinstance(ray, np.ndarray):
-        raise error.SigMFError('Argument must be a numpy array')
+        raise error.SigMFError("Argument must be a numpy array")
     atype = ray.dtype
-    if atype.kind not in ('u', 'i', 'f', 'c'):
-        raise error.SigMFError('Unsupported data type:', atype)
-    data_type_str = ''
-    if atype.kind == 'c':
-        data_type_str += 'cf'
+    if atype.kind not in ("u", "i", "f", "c"):
+        raise error.SigMFError("Unsupported data type:", atype)
+    data_type_str = ""
+    if atype.kind == "c":
+        data_type_str += "cf"
         # units are component bits, numpy complex types len(I)+len(Q)
         data_type_str += str(atype.itemsize * 8 // 2)
-    elif atype.kind == 'f':
-        data_type_str += 'rf'
-        data_type_str += str(atype.itemsize * 8)  # units are bits
-    elif atype.kind in ('u', 'i'):
-        data_type_str += 'r' + atype.kind
-        data_type_str += str(atype.itemsize * 8)  # units are bits
-    if (atype.itemsize > 1):
+    elif atype.kind == "f":
+        data_type_str += "rf"
+        data_type_str += str(atype.itemsize * 8)  # itemsize in bits
+    elif atype.kind in ("u", "i"):
+        data_type_str += "r" + atype.kind
+        data_type_str += str(atype.itemsize * 8)  # itemsize in bits
+    if atype.itemsize > 1:
         # only append endianness for types over 8 bits
         data_type_str += get_endian_str(ray)
     return data_type_str