Can now read GAMS variables and convert them into pandas DataFrames

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.2.0] - 2022-07-02
+### Added
+* Added the possibility to read GAMS variables and convert them into pandas DataFrames
+
 ## [2.1.1] - 2020-08-20
 ### Added
 * Add index names from symbol domain if defined when converting to a pandas object.

gdx2py/__init__.py

@@ -2,4 +2,4 @@
 
 from .version import __version__
 from .gdxfile import GdxFile
-from .gams import GAMSSet, GAMSScalar, GAMSParameter
+from .gams import GAMSSet, GAMSScalar, GAMSParameter, GAMSVariable

gdx2py/gams.py

@@ -250,3 +250,79 @@ def to_pandas(self):
 
         return df
 
+
+class GAMSVariable(_GAMSNDimSymbol):
+    """Class for GAMS Variables
+
+    Attributes:
+        domain (list): List of set names that make the domain of the symbol
+        expl_text (str): Symbol explanatory text
+
+    Methods:
+        keys: Return a view to the symbol's keys
+        values: Return a view to the symbol's values
+    """
+
+    def __init__(
+            self,
+            data: Mapping[tuple, float],
+            domain: Sequence[str] = None,
+            expl_text: str = '',
+    ):
+        """Constructor for GAMSParameter
+
+        Args:
+            data: Dictionay of keys and values
+            domain (optional): List of domain set names, use `None` for the universal set
+            expl_text (optional): Explanatory text
+
+        Raises:
+            ValueError
+        """
+
+        # Check arguments
+        try:
+            super().__init__(data.keys(), domain, expl_text)
+        except AttributeError:
+            raise ValueError("Data must be a mapping")
+        self._type = 'Parameter'
+        self._data = data
+
+    def keys(self):
+        return self._data.keys()
+
+    def values(self):
+        try:
+            return self._data.values()
+        except TypeError:  # Support self.data being a pandas.Series
+            return self._data.values
+
+    def __getitem__(self, key):
+        return self._data[key]
+
+    def __iter__(self):
+        self._iterator = iter(self._data.items())
+        return self
+
+    def __next__(self):
+        key, val = next(self._iterator)
+        return key, float(val)
+
+    def to_pandas(self):
+        try:
+            import pandas as pd
+        except ImportError:
+            raise ImportError(
+                "This feature needs pandas package. "
+                "Please use pip or conda to install pandas"
+            )
+        df = pd.DataFrame(iter(self.values()), self.keys())
+        df.name = self.expl_text
+
+        if self.domain:
+            if isinstance(df.index, pd.MultiIndex):
+                df.index.names = self.domain
+            else:
+                df.index.name = self.domain[0]
+
+        return df

gdx2py/gdxfile.py

@@ -4,28 +4,28 @@
 
 __author__ = "Erkka Rinne"
 
-
 import sys
 import os.path
 import math
 from copy import copy
 from warnings import warn
 from collections.abc import Mapping, Sequence, KeysView, ValuesView
 
-from gdxcc import GMS_VAL_LEVEL, GMS_DT_SET, GMS_DT_PAR
+from gdxcc import GMS_VAL_LEVEL, GMS_VAL_MARGINAL, GMS_VAL_LOWER, GMS_VAL_UPPER, \
+    GMS_DT_SET, GMS_DT_PAR, GMS_DT_VAR
 import gdxcc
 
-from .gams import _GAMSSymbol, GAMSSet, GAMSScalar, GAMSParameter
+from .gams import _GAMSSymbol, GAMSSet, GAMSScalar, GAMSParameter, GAMSVariable
 
 # String representations of API constants
 GMS_DTYPES = {
     'Set': GMS_DT_SET,
     'Parameter': GMS_DT_PAR,
     'Scalar': GMS_DT_PAR,
     # Not used at the moments
-    #'Variable': GMS_DT_VAR,
-    #'Equation': GMS_DT_EQU,
-    #'Alias': GMS_DT_ALIAS:
+    'Variable': GMS_DT_VAR,
+    # 'Equation': GMS_DT_EQU,
+    # 'Alias': GMS_DT_ALIAS:
 }
 
 # Define data types
@@ -47,6 +47,13 @@
     gdxcc.GMS_SV_NAINT: math.nan,
 }
 
+VARIABLE_DIMENSIONS = {
+    GMS_VAL_LEVEL: "level",
+    GMS_VAL_MARGINAL: "marginal",
+    GMS_VAL_LOWER: "lower bound",
+    GMS_VAL_UPPER: "upper bound"
+}
+
 GMS_USERINFO_SET_PARAMETER = 0  # UserInfo value for sets and parameters
 
 
@@ -346,6 +353,19 @@ def _read_symbol(self, symno: int):
                 )  # Squeze out dimension of 1-dim keys
                 val = value_arr[GMS_VAL_LEVEL]
                 values[i] = SPECIAL_VALUES.get(val, val)
+        elif symtype == GMS_DT_VAR:
+            for i in range(recs):
+                _ret, key_arr, value_arr, _afdim = gdxcc.gdxDataReadStr(self._h)
+                keys[i] = (
+                    key_arr[0] if dim == 1 else tuple(key_arr)
+                )  # Squeze out dimension of 1-dim keys
+
+                value = {}
+                for elem in VARIABLE_DIMENSIONS:
+                    val = value_arr[elem]
+                    value[VARIABLE_DIMENSIONS[elem]] = SPECIAL_VALUES.get(val, val)
+
+                values[i] = value
 
         # Done reading
         gdxcc.gdxDataReadDone(self._h)
@@ -360,6 +380,10 @@ def _read_symbol(self, symno: int):
                 return GAMSParameter(
                     dict(zip(keys, values)), domain=domain, expl_text=expl_text
                 )
+        elif symtype == GMS_DT_VAR:
+            return GAMSVariable(
+                dict(zip(keys, values)), domain=domain, expl_text=expl_text
+            )
 
     def _write_symbol(self, symname: str, symbol: _GAMSSymbol):
         """Write a Pandas series to a GAMS Set symbol
@@ -369,8 +393,12 @@ def _write_symbol(self, symname: str, symbol: _GAMSSymbol):
 
         Raises:
             RuntimeError
+            NotImplementedError
         """
 
+        if isinstance(symbol, GAMSVariable):
+            raise NotImplementedError
+
         # Get number of dimensions
         dim = symbol.dimension
 

gdx2py/version.py

@@ -1 +1 @@
-__version__ = '2.1.1'
+__version__ = '2.2.0'