Parse all components of ISO 8601 durations, even if S is not included

Author: mgmarino

pandas/_libs/tslibs/timedeltas.pyx

@@ -620,9 +620,6 @@ cdef inline int64_t parse_iso_format_string(str ts) except? -1:
             if not len(unit):
                 number.append(c)
             else:
-                if 'H' in unit or 'M' in unit or 'W' in unit:
-                    if len(number) > 2:
-                        raise ValueError(err_msg)
                 r = timedelta_from_spec(number, '0', unit)
                 result += timedelta_as_neg(r, neg)
 
@@ -638,6 +635,13 @@ cdef inline int64_t parse_iso_format_string(str ts) except? -1:
                     neg = 1
             elif c in ['W', 'D', 'H', 'M']:
                 unit.append(c)
+                if c in ['H', 'M'] and len(number) > 2:
+                    raise ValueError(err_msg)
+                r = timedelta_from_spec(number, '0', unit)
+                result += timedelta_as_neg(r, neg)
+
+                neg = 0
+                unit, number = [], []
             elif c == '.':
                 # append any seconds
                 if len(number):

pandas/tests/scalar/timedelta/test_constructors.py

@@ -231,6 +231,9 @@ def test_overflow_on_construction():
         ("PT1S", Timedelta(seconds=1)),
         ("PT0S", Timedelta(seconds=0)),
         ("P1WT0S", Timedelta(days=7, seconds=0)),
+        ("P1D", Timedelta(days=1)),
+        ("P1DT1H", Timedelta(days=1, hours=1)),
+        ("P1W", Timedelta(days=7)),
     ],
 )
 def test_iso_constructor(fmt, exp):