create csv handler that uses similar logic to yaml_from_file

Author: lily-tomkovic-DWR

schimpy/util/yaml_load.py

@@ -1,5 +1,50 @@
 from schimpy.schism_yaml import load, dump
 from pathlib import Path
+import pandas as pd
+import string
+
+
+def csv_from_file(filename, envvar=None, **kwargs):
+    """
+    Load a CSV file and substitute environment variables in string fields.
+
+    Parameters
+    ----------
+    filename : str
+        Path to the CSV file.
+    envvar : dict, optional
+        Dictionary of variables to substitute (e.g., {'calsim_dss': 'blah.dss'}).
+    kwargs : passed to pd.read_csv
+
+    Returns
+    -------
+    pd.DataFrame
+        DataFrame with substitutions applied.
+    """
+    df = pd.read_csv(filename, **kwargs)
+    if envvar is None:
+        return df
+
+    # Substitute in column names
+    df.columns = [
+        string.Template(str(col)).safe_substitute(**envvar) for col in df.columns
+    ]
+
+    # Substitute in index (if it's string/object)
+    if df.index.dtype == "object":
+        df.index = [
+            string.Template(str(idx)).safe_substitute(**envvar) for idx in df.index
+        ]
+
+    # Substitute in all string/object cells
+    for col in df.select_dtypes(include=["object"]).columns:
+        df[col] = (
+            df[col]
+            .astype(str)
+            .apply(lambda x: string.Template(x).safe_substitute(**envvar))
+        )
+
+    return df
 
 
 def yaml_from_file(filename, envvar=None):