Minor refactoring

Move calculation of interval_length to units module.

syfop/network.py

@@ -3,12 +3,11 @@
 
 import linopy
 import networkx as nx
-import numpy as np
 import pandas as pd
 from networkx.drawing.nx_agraph import graphviz_layout
 
 from syfop.node_base import NodeInputBase, NodeOutputBase
-from syfop.units import default_units, ureg
+from syfop.units import default_units, interval_length, ureg
 from syfop.util import DEFAULT_NUM_TIME_STEPS, timeseries_variable
 
 
@@ -360,25 +359,22 @@ def total_costs(self):
                 continue
             input_flows = list(node.input_flows.values())
             assert len(input_flows) == 1, "only one input_flow is supported"
+            input_flow = input_flows[0]
 
             # this is just a check: atm we support only Node, so input_flows should be plain linopy
             # variables without units, but in case of a NodeScalableInput or a NodeFixInput we
             # would need to strip units here and use the magnitude.
             assert isinstance(input_flows[0], linopy.Variable), "unexpected input_flow type"
 
-            # see also https://stackoverflow.com/a/78373992/859591
-            interval_lengths = np.diff(self.time_coords)
-            # this works only if equidistant... should have been checked before already.
-            assert (interval_lengths == interval_lengths[0]).all(), "timestes are not equidistant"
-            interval_length_h = interval_lengths[0] / np.timedelta64(1, "h")
+            interval_length_h = interval_length(self.time_coords).to(ureg.h).magnitude
 
             input_flow_unit = default_units[node.input_commodities[0]]  # something like MW
             input_flow_costs_mag = node.input_flow_costs.to(
                 self.total_cost_unit / (input_flow_unit * ureg.h)
             ).magnitude
 
             # something like: EUR/MWh * x h * MW
-            costs = costs + input_flow_costs_mag * interval_length_h * input_flows[0].sum()
+            costs = costs + input_flow_costs_mag * interval_length_h * input_flow.sum()
 
         costs = costs + storage_costs
 

syfop/units.py

@@ -1,3 +1,4 @@
+import numpy as np
 import pint
 import pint_xarray  # noqa: F401
 
@@ -50,3 +51,13 @@ def strip_unit(x, commodity):
         return x.to(default_units[commodity]).magnitude
     else:
         return x
+
+
+def interval_length(time_coords):
+    # see also https://stackoverflow.com/a/78373992/859591
+    interval_lengths = np.diff(time_coords)
+    # this works only if equidistant... should have been checked before already.
+    assert (interval_lengths == interval_lengths[0]).all(), "timestes are not equidistant"
+    interval_length_h = interval_lengths[0] / np.timedelta64(1, "h")
+
+    return interval_length_h * ureg.h