Merge pull request microsoft#1629 from WilliamHPNielsen/feature/time_…

…parameter

Feature : an elapsed time parameter

docs/api/parameters/index.rst

@@ -7,6 +7,7 @@ qcodes.instrument (Parameters)
 
     qcodes.instrument.parameter
     qcodes.instrument.group_parameter
+    qcodes.instrument.specialized_parameters
 
 
 .. automodule:: qcodes.instrument
@@ -18,3 +19,4 @@ qcodes.instrument (Parameters)
 
    parameter
    group_parameter
+   specialized_parameters

docs/api/parameters/specialized_parameters.rst

@@ -0,0 +1,6 @@
+qcodes.instrument.specialized_parameters
+----------------------------------------
+
+
+.. automodule:: qcodes.instrument.specialized_parameters
+   :members:

qcodes/dataset/__init__.py

@@ -1 +1,8 @@
+"""
+The dataset module contains code related to storage and retrieval of data to
+and from disk
+"""
 
+# flake8: noqa (we don't need the "<...> imported but unused" error)
+
+from qcodes.dataset.sqlite.database import initialise_or_create_database_at

qcodes/instrument/specialized_parameters.py

@@ -0,0 +1,48 @@
+"""
+Module for specialized parameters. The qcodes.instrument.parameters module
+provides generic parameters for different generic cases. This module provides
+useful/convenient specializations of such generic parameters.
+"""
+
+from time import perf_counter
+
+from qcodes.instrument.parameter import Parameter
+
+
+class ElapsedTimeParameter(Parameter):
+    """
+    Parameter to measure elapsed time. Measures wall clock time since the
+    last reset of the instance's clock. The clock is reset upon creation of the
+    instance. The constructor passes kwargs along to the Parameter constructor.
+
+    Args:
+        name: the local name of the parameter. See the documentation of
+            :class:`qcodes.instrument.parameter.Parameter` for more details.
+    """
+
+    def __init__(self, name: str, label: str = 'Elapsed time', **kwargs):
+
+        hardcoded_kwargs = ['unit', 'get_cmd', 'set_cmd']
+
+        for hck in hardcoded_kwargs:
+            if hck in kwargs:
+                raise ValueError(f'Can not set "{hck}" for an '
+                                 'ElapsedTimeParameter.')
+
+        super().__init__(name=name,
+                         label=label,
+                         unit='s',
+                         set_cmd=False,
+                         **kwargs)
+
+        self._t0: float = perf_counter()
+
+    def get_raw(self) -> float:
+        return perf_counter() - self.t0
+
+    def reset_clock(self) -> None:
+        self._t0 = perf_counter()
+
+    @property
+    def t0(self) -> float:
+        return self._t0

qcodes/tests/test_specialized_parameters.py

@@ -0,0 +1,58 @@
+"""
+Tests for the specialized_parameters module
+"""
+
+from time import sleep
+
+import pytest
+
+from qcodes.instrument.specialized_parameters import ElapsedTimeParameter
+
+
+def test_elapsed_time_parameter_init():
+
+    tp1 = ElapsedTimeParameter('time1')
+    sleep(0.01)
+    tp2 = ElapsedTimeParameter('time2')
+
+    assert tp1() > tp2()
+
+
+def test_elapsed_time_parameter_monotonic():
+
+    tp = ElapsedTimeParameter('time')
+
+    times = [tp() for _ in range(25)]
+
+    assert sorted(times) == times
+
+
+def test_elapsed_time_parameter_reset_clock():
+
+    tp = ElapsedTimeParameter('time')
+
+    sleep(0.01)
+    t1 = tp()
+
+    tp.reset_clock()
+    t2 = tp()
+
+    assert t1 > t2
+
+
+def test_elapsed_time_parameter_not_settable():
+
+    tp = ElapsedTimeParameter('time')
+
+    with pytest.raises(NotImplementedError):
+        tp(0)
+
+
+def test_elapsed_time_parameter_forbidden_kwargs():
+
+    forbidden_kwargs = ['unit', 'get_cmd', 'set_cmd']
+
+    for fb_kwarg in forbidden_kwargs:
+        match = f'Can not set "{fb_kwarg}" for an ElapsedTimeParameter'
+        with pytest.raises(ValueError, match=match):
+            ElapsedTimeParameter('time', **{fb_kwarg: None})