add proper typechecking for nu & mu values

hoomd/data/typeconverter.py

@@ -106,6 +106,19 @@ def nonnegative_real(number):
     return float_number
 
 
+def positive_int(number):
+    """Ensures that a value is a positive integer"""
+    if isinstance(number, float) and not number.is_integer():
+        raise TypeConversionError(f"Expected integer, {number} has a non-zero decimal part")
+    try:
+        int_number = int(number)
+    except Exception as err:
+        raise TypeConversionError(f"{number} is not convertible to int.") from err
+    if int_number <= 0:
+        raise TypeConversionError("Expected a positive integer")
+    return int_number
+
+
 def identity(value):
     """Return the given value."""
     return value

hoomd/md/pair/pair.py

@@ -12,7 +12,7 @@
 from hoomd.data.parameterdicts import ParameterDict, TypeParameterDict
 from hoomd.data.typeparam import TypeParameter
 import numpy as np
-from hoomd.data.typeconverter import OnlyFrom, nonnegative_real, positive_real
+from hoomd.data.typeconverter import OnlyFrom, nonnegative_real, positive_real, positive_int
 
 
 class Pair(force.Force):
@@ -2099,7 +2099,7 @@ def __init__(self, nlist, default_r_cut=None, default_r_on=0.0, mode="none"):
             "params",
             "particle_types",
             TypeParameterDict(
-                epsilon=float, sigma=float, R=float, mu=int, nu=int, len_keys=2
+                epsilon=float, sigma=float, R=float, mu=positive_int, nu=positive_int, len_keys=2
             ),
         )