Draft: Resolve "Use Numpy arrays instead of `ForEachObject` instances"

Closes #34 (closed)

lisainstrument/indexing.py

+#! /usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Utility functions for indexing MOSAs and SC.
+
+Authors:
+    Jean-Baptiste Bayle <j2b.bayle@gmail.com>
+"""
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+"""List of MOSA index as two-figure strings, in the order they are used in an array."""
+MOSAS = ['12', '23', '31', '13', '32', '21']
+
+
+def index2mosa(index):
+    """Return MOSA index associated with a given array index.
+
+    Args:
+        index: array index
+
+    Returns:
+        MOSA index as a two-figure string, e.g., '12'.
+    """
+    try:
+        return MOSAS[index]
+    except IndexError as error:
+        raise IndexError(f"invalid array index '{index}' for MOSA") from error
+
+
+def mosa2index(mosa):
+    """Return array index associated with a given MOSA index.
+
+    Args:
+        mosa: MOSA index as a two-figure string or integer
+
+    Returns:
+        Array index as an integer.
+    """
+    try:
+        return MOSAS.index(str(mosa))
+    except ValueError as error:
+        raise ValueError(f"invalid MOSA index '{mosa}'") from error
+
+
+MOSA12 = mosa2index('12')
+MOSA23 = mosa2index('23')
+MOSA31 = mosa2index('31')
+MOSA13 = mosa2index('13')
+MOSA32 = mosa2index('32')
+MOSA21 = mosa2index('21')
+
+
+"""List of SC indices as one-figure strings, in the order they are used in an array."""
+SC = ['1', '2', '3']
+
+
+def index2sc(index):
+    """Return SC index associated with a given array index.
+
+    Args:
+        index: array index
+
+    Returns:
+        SC index as a one-figure string, e.g., '1'.
+    """
+    try:
+        return SC[index]
+    except IndexError as error:
+        raise IndexError(f"invalid array index '{index}' for SC") from error
+
+
+def sc2index(mosa):
+    """Return array index associated with a given SC index.
+
+    Args:
+        mosa: SC index as a one-figure string, or integer
+
+    Returns:
+        Array index as an integer.
+    """
+    try:
+        return SC.index(str(mosa))
+    except ValueError as error:
+        raise ValueError(f"invalid SC index '{mosa}'") from error
+
+
+SC1 = sc2index(1)
+SC2 = sc2index(2)
+SC3 = sc2index(3)