Add to_ixmp4() method

RELEASE_NOTES.md

@@ -1,6 +1,7 @@
-# Next Release
+# Next release
 
 - [#813](https://github.com/IAMconsortium/pyam/pull/813) Fix a corner case in region-aggregation with missing data
+- [#797](https://github.com/IAMconsortium/pyam/pull/797) Add `to_ixmp4()` method to write to an **ixmp4** platform
 
 # Release v2.1.0
 

pyam/core.py

@@ -11,6 +11,9 @@
 from pathlib import Path
 from tempfile import TemporaryDirectory
 
+import ixmp4
+
+from pyam.ixmp4 import write_to_ixmp4
 from pyam.slice import IamSlice
 from pyam.filter import filter_by_time_domain, filter_by_year, filter_by_dt_arg
 
@@ -2333,6 +2336,16 @@ def diff(self, mapping, periods=1, append=False):
         # append to `self` or return as `IamDataFrame`
         return self._finalize(_value, append=append)
 
+    def to_ixmp4(self, platform: ixmp4.Platform):
+        """Save all scenarios as new default runs in an ixmp4 platform database instance
+
+        Parameters
+        ----------
+        platform : :class:`ixmp4.Platform` or str
+            The ixmp4 platform database instance to which the scenario data is saved
+        """
+        write_to_ixmp4(platform, self)
+
     def _to_file_format(self, iamc_index):
         """Return a dataframe suitable for writing to a file"""
         df = self.timeseries(iamc_index=iamc_index).reset_index()

pyam/ixmp4.py

@@ -0,0 +1,42 @@
+import ixmp4
+from ixmp4.core.region import RegionModel
+from ixmp4.core.unit import UnitModel
+
+
+def write_to_ixmp4(platform: ixmp4.Platform | str, df):
+    """Save all scenarios as new default runs in an ixmp4 platform database instance
+
+    Parameters
+    ----------
+    platform : :class:`ixmp4.Platform` or str
+        The ixmp4 platform database instance to which the scenario data is saved
+    df : pyam.IamDataFrame
+        The IamDataFrame instance with scenario data
+    """
+    if df.time_domain != "year":
+        raise NotImplementedError("Only time_domain='year' is supported for now")
+
+    if not isinstance(platform, ixmp4.Platform):
+        platform = ixmp4.Platform(platform)
+
+    # TODO: implement a try-except to roll back changes if any error writing to platform
+    # depends on https://github.com/iiasa/ixmp4/issues/29
+    # quickfix: ensure that units and regions exist before writing
+    for dimension, values, model in [
+        ("regions", df.region, RegionModel),
+        ("units", df.unit, UnitModel),
+    ]:
+        platform_values = platform.__getattribute__(dimension).tabulate().name.values
+        if missing := [i for i in values if i not in platform_values]:
+            raise model.NotFound(
+                ", ".join(missing)
+                + f". Use `Platform.{dimension}.create()` to add the missing {dimension}."
+            )
+
+    for model, scenario in df.index:
+        _df = df.filter(model=model, scenario=scenario)
+
+        run = platform.runs.create(model=model, scenario=scenario)
+        run.iamc.add(_df.data)
+        run.meta = dict(_df.meta.iloc[0])
+        run.set_as_default()

pyam/utils.py

@@ -228,7 +228,7 @@ def _intuit_column_groups(df, index, include_index=False):
     elif isinstance(df, pd.DataFrame):
         existing_cols = existing_cols.union(df.columns)
 
-    # check that there is no column in the timeseries data with reserved names
+    # check that there is no unnamed column in the timeseries data
     if None in existing_cols:
         raise ValueError("Unnamed column in timeseries data: None")
 

setup.cfg

@@ -27,7 +27,7 @@ python_requires = >=3.10, <3.12
 # Please also add a section "Dependency changes" to the release notes
 install_requires =
     iam-units >= 2020.4.21
-    ixmp4 >= 0.4.0
+    ixmp4 >= 0.6.0
     numpy >= 1.23.0, < 1.24
 #    requests  included via ixmp4
 #    httpx[http2] included via ixmp4

tests/test_ixmp4.py

@@ -0,0 +1,35 @@
+import pytest
+from ixmp4.core import Platform
+from ixmp4.data.backend import SqliteTestBackend
+from ixmp4.core.region import RegionModel
+from ixmp4.core.unit import UnitModel
+
+
+def test_to_ixmp4_missing_region_raises(test_df_year):
+    """Writing to platform raises if region not defined"""
+    platform = Platform(_backend=SqliteTestBackend())
+    with pytest.raises(RegionModel.NotFound, match="World. Use `Platform.regions."):
+        test_df_year.to_ixmp4(platform=platform)
+
+
+def test_to_ixmp4_missing_unit_raises(test_df_year):
+    """Writing to platform raises if unit not defined"""
+    platform = Platform(_backend=SqliteTestBackend())
+    platform.regions.create(name="World", hierarchy="common")
+    with pytest.raises(UnitModel.NotFound, match="EJ/yr. Use `Platform.units."):
+        test_df_year.to_ixmp4(platform=platform)
+
+
+def test_ixmp4_integration(test_df):
+    """Write an IamDataFrame to the platform"""
+    platform = Platform(_backend=SqliteTestBackend())
+    platform.regions.create(name="World", hierarchy="common")
+    platform.units.create(name="EJ/yr")
+
+    if test_df.time_domain == "year":
+        test_df.to_ixmp4(platform=platform)
+    else:
+        with pytest.raises(NotImplementedError):
+            test_df.to_ixmp4(platform=platform)
+
+    # TODO add test for reading data from ixmp4 platform