diff --git a/Blocks/CMakeLists.txt b/Blocks/CMakeLists.txt
new file mode 100644
index 0000000..21c2793
--- /dev/null
+++ b/Blocks/CMakeLists.txt
@@ -0,0 +1,13 @@
+########################################################################
+## Build and install
+########################################################################
+POTHOS_PYTHON_UTIL(
+    TARGET PythonBlocks
+    SOURCES
+        __init__.py
+        Evaluator.py
+    FACTORIES
+        "/python/evaluator:Evaluator"
+    DESTINATION PothosBlocks
+    ENABLE_DOCS
+)
diff --git a/Blocks/Evaluator.py b/Blocks/Evaluator.py
new file mode 100644
index 0000000..39c2827
--- /dev/null
+++ b/Blocks/Evaluator.py
@@ -0,0 +1,167 @@
+# Copyright (c) 2020-2021 Nicholas Corgan
+# SPDX-License-Identifier: BSL-1.0
+
+from functools import partial
+import importlib
+
+import Pothos
+
+"""
+/***********************************************************************
+ * |PothosDoc Python Evaluator
+ *
+ * The Python evaluator block performs a user-specified expression evaluation
+ * on input slot(s) and produces the evaluation result on an output signal.
+ * The input slots are user-defined. The output signal is named "triggered".
+ * The arguments from the input slots must be primitive types.
+ *
+ * |category /Event
+ * |keywords signal slot eval expression
+ *
+ * |param imports[Imports] A list of Python modules to import before executing the expression.
+ * Example: ["math", "numpy"] will import the math and numpy modules.
+ * |default ["math"]
+ *
+ * |param args[Arguments] A list of named variables to use in the expression.
+ * Each variable corresponds to settings slot on the transform block.
+ * Example: ["foo", "bar"] will create the slots "setFoo" and "setBar".
+ * |default ["val"]
+ *
+ * |param expr[Expression] The expression to re-evaluate for each slot event.
+ * An expression is valid Python, comprised of combinations of variables, constants, and math functions.
+ * Example: math.log2(foo)/bar
+ *
+ * <p><b>Multi-argument input:</b> Upstream blocks may pass multiple arguments to a slot.
+ * Each argument will be available to the expression suffixed by its argument index.
+ * For example, suppose that the slot "setBaz" has two arguments,
+ * then the following expression would use both arguments: "baz0 + baz1"</p>
+ *
+ * |default "math.log2(val)"
+ * |widget StringEntry()
+ *
+ * |param localVars[LocalVars] A map of variable names to values.
+ * This allows you to use global variables from the topology in the expression.
+ *
+ * For example this mapping lets us use foo, bar, and baz in the expression
+ * to represent several different globals and combinations of expressions:
+ * {"foo": myGlobal, "bar": "test123", "baz": myNum+12345}
+ * |default {}
+ * |preview valid
+ *
+ * |factory /python/evaluator(args)
+ * |setter setExpression(expr)
+ * |setter setImports(imports)
+ * |setter setLocalVars(localVars)
+ **********************************************************************/
+"""
+class Evaluator(Pothos.Block):
+    def __init__(self, varNames):
+        Pothos.Block.__init__(self)
+        self.setName("/python/evaluator")
+
+        self.__checkIsStringList(varNames)
+
+        self.__expr = ""
+        self.__localVars = dict()
+        self.__varNames = varNames
+        self.__varValues = dict()
+        self.__imports = []
+        self.__varsReady = set()
+
+        # Add setters for user variables
+        for name in self.__varNames:
+            if not name:
+                continue
+
+            setterName = "set"+name[0].upper()+name[1:]
+            setattr(Evaluator, setterName, partial(self.__setter, name))
+            self.registerSlot(setterName)
+
+        self.registerSlot("setExpression")
+        self.registerSlot("setImports")
+        self.registerSlot("setLocalVars")
+        self.registerSignal("triggered")
+
+    def getExpression(self):
+        return self.__expr
+
+    def setExpression(self,expr):
+        self.__checkIsStr(expr)
+        self.__expr = expr
+
+        notReadyVars = [var for var in self.__varNames if var not in self.__varsReady]
+        if notReadyVars:
+            return
+
+        args = self.__performEval()
+        self.triggered(args)
+
+    def setImports(self,imports):
+        self.__checkIsStringOrStringList(imports)
+        self.__imports = imports if (type(imports) == list) else [imports]
+
+    def getImports(self):
+        return self.__imports
+
+    def setLocalVars(self,userLocalVars):
+        self.__checkIsDict(userLocalVars)
+        self.__localVars = userLocalVars
+
+    #
+    # Private utility functions
+    #
+
+    def __performEval(self):
+        for key,val in self.__varValues.items():
+            locals()[key] = val
+
+        for mod in self.__imports:
+            exec("import "+mod)
+
+        for key,val in self.__localVars.items():
+            locals()[key] = val
+
+        return eval(self.__expr)
+
+    def __setter(self,field,*args):
+        if len(args) > 1:
+            for i in range(len(args)):
+                self.__varValues[field+str(i)] = args[i]
+        else:
+            self.__varValues[field] = args[0]
+
+        self.__varsReady.add(field)
+
+        notReadyVars = [var for var in self.__varNames if var not in self.__varsReady]
+        if (not notReadyVars) and self.__expr:
+            args = self.__performEval()
+            self.triggered(args)
+
+        return None
+
+    def __checkIsStr(self,var):
+        if type(var) != str:
+            raise ValueError("The given value must be a str. Found {0}".format(type(var)))
+
+    def __checkIsDict(self,var):
+        if type(var) != dict:
+            raise ValueError("The given value must be a dict. Found {0}".format(type(var)))
+
+    def __checkIsList(self,var):
+        if type(var) != list:
+            raise ValueError("The given value must be a list. Found {0}".format(type(var)))
+
+    def __checkIsStringList(self,var):
+        self.__checkIsList(var)
+
+        nonStringVals = [x for x in var if type(x) != str]
+        if nonStringVals:
+            raise ValueError("All list values must be strings. Found {0}".format(type(nonStringVals[0])))
+
+    def __checkIsStringOrStringList(self,var):
+        if type(var) is str:
+            return
+        elif type(var) is list:
+            self.__checkIsStringList(var)
+        else:
+            raise ValueError("The given value must be a string or list. Found {0}".format(type(var)))
diff --git a/Blocks/__init__.py b/Blocks/__init__.py
new file mode 100644
index 0000000..4c8603f
--- /dev/null
+++ b/Blocks/__init__.py
@@ -0,0 +1,4 @@
+# Copyright (c) 2020-2021 Nicholas Corgan
+# SPDX-License-Identifier: BSL-1.0
+
+from . Evaluator import Evaluator
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 86734e9..799f682 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -141,4 +141,5 @@ install(
 # Enter the subdirectory configuration
 ########################################################################
 add_subdirectory(Pothos)
+add_subdirectory(Blocks)
 add_subdirectory(TestBlocks)
diff --git a/Pothos/__init__.py b/Pothos/__init__.py
index a1f106f..4a2213c 100644
--- a/Pothos/__init__.py
+++ b/Pothos/__init__.py
@@ -1,5 +1,5 @@
 # Copyright (c) 2014-2016 Josh Blum
-#                    2019 Nicholas Corgan
+#               2019-2020 Nicholas Corgan
 # SPDX-License-Identifier: BSL-1.0
 
 from . PothosModule import *
diff --git a/TestPythonBlock.cpp b/TestPythonBlock.cpp
index 76d1c1e..ae2a06d 100644
--- a/TestPythonBlock.cpp
+++ b/TestPythonBlock.cpp
@@ -1,13 +1,22 @@
 // Copyright (c) 2014-2017 Josh Blum
+//               2020-2021 Nicholas Corgan
 // SPDX-License-Identifier: BSL-1.0
 
 #include <Pothos/Framework.hpp>
 #include <Pothos/Managed.hpp>
 #include <Pothos/Testing.hpp>
 #include <Pothos/Proxy.hpp>
-#include <iostream>
+
 #include <json.hpp>
 
+#include <Poco/Path.h>
+#include <Poco/TemporaryFile.h>
+#include <Poco/Thread.h>
+
+#include <complex>
+#include <cmath>
+#include <iostream>
+
 using json = nlohmann::json;
 
 POTHOS_TEST_BLOCK("/proxy/python/tests", python_module_import)
@@ -68,3 +77,88 @@ POTHOS_TEST_BLOCK("/proxy/python/tests", test_signals_and_slots)
     std::string lastWord = acceptor.call("getLastWord");
     POTHOS_TEST_EQUAL(lastWord, "hello");
 }
+
+//
+// Test utility blocks
+//
+
+static Pothos::Object performEval(const Pothos::Proxy& evaluator, const std::string& expr)
+{
+    auto periodicTrigger = Pothos::BlockRegistry::make("/blocks/periodic_trigger");
+    periodicTrigger.call("setRate", 5); // Triggers per second
+    periodicTrigger.call("setArgs", std::vector<std::string>{expr});
+
+    auto slotToMessage = Pothos::BlockRegistry::make(
+                             "/blocks/slot_to_message",
+                             "handleIt");
+    auto collectorSink = Pothos::BlockRegistry::make(
+                            "/blocks/collector_sink",
+                            ""); // DType irrelevant
+
+    {
+        Pothos::Topology topology;
+
+        topology.connect(periodicTrigger, "triggered", evaluator, "setExpression");
+        topology.connect(evaluator, "triggered", slotToMessage, "handleIt");
+        topology.connect(slotToMessage, 0, collectorSink, 0);
+
+        // Since periodic_trigger will trigger 5 times/second, half a second
+        // should be enough to get at least one.
+        topology.commit();
+        Poco::Thread::sleep(500); // ms
+    }
+
+    auto collectorSinkObjs = collectorSink.call<Pothos::ObjectVector>("getMessages");
+    POTHOS_TEST_FALSE(collectorSinkObjs.empty());
+
+    return collectorSinkObjs[0];
+}
+
+POTHOS_TEST_BLOCK("/proxy/python/tests", test_evaluator)
+{
+    constexpr auto jsonStr = "{\"outer\": [{\"inner\": [400,300,200,100]}, {\"inner\": [0.1,0.2,0.3,0.4]}]}";
+    constexpr auto inner0Index = 3;
+    constexpr auto inner1Index = 2;
+    const auto localDoubles = std::vector<double>{12.3456789, 0.987654321};
+    const std::complex<double> complexArg{1.351, 4.18};
+    constexpr double doubleArg0 = 1234.0;
+    constexpr double doubleArg1 = 5678.0;
+
+    auto cppJSON = json::parse(jsonStr);
+
+    const auto expectedResult = (cppJSON["outer"][0]["inner"][inner0Index].get<double>()
+                              * cppJSON["outer"][1]["inner"][inner1Index].get<double>())
+                              + std::pow((localDoubles[0] - std::pow(localDoubles[1] + std::abs(complexArg), 2)), 3)
+                              - doubleArg0
+                              + doubleArg1;
+
+    auto evaluator = Pothos::BlockRegistry::make(
+                         "/python/evaluator",
+                         std::vector<std::string>{"inner0Index", "inner1Index", "complexArg", "doubleArg"});
+    evaluator.call("setInner0Index", inner0Index);
+    evaluator.call("setInner1Index", inner1Index);
+    evaluator.call("setComplexArg", complexArg);
+    evaluator.call("setDoubleArg", doubleArg0, doubleArg1);
+
+    auto imports = std::vector<std::string>{"json","math","numpy"};
+    evaluator.call("setImports", imports);
+
+    auto env = Pothos::ProxyEnvironment::make("python");
+    auto localVars = Pothos::ProxyMap
+    {
+        {env->makeProxy("testJSON"), env->makeProxy(jsonStr)},
+        {env->makeProxy("localDoubles"), env->makeProxy(localDoubles)}
+    };
+    evaluator.call("setLocalVars", localVars);
+
+    const std::string jsonExpr0 = "json.loads(testJSON)['outer'][0]['inner'][inner0Index]";
+    const std::string jsonExpr1 = "json.loads(testJSON)['outer'][1]['inner'][inner1Index]";
+    const std::string powExpr = "numpy.power([localDoubles[0] - math.pow(localDoubles[1] + abs(complexArg), 2)], 3)[0]";
+    const auto expr = jsonExpr0 + " * " + jsonExpr1 + " + " + powExpr + "- doubleArg0 + doubleArg1";
+
+    auto result = performEval(evaluator, expr);
+    POTHOS_TEST_CLOSE(
+        expectedResult,
+        result.convert<double>(),
+        1e-3);
+}