diff --git a/Phys/FunctorCore/include/Functors/Function.h b/Phys/FunctorCore/include/Functors/Function.h
index 0da4569cbd6a7cd30c6b339231276b185546d5bf..ff8fb84edf57087029157a3866285978bc9cedc2 100644
--- a/Phys/FunctorCore/include/Functors/Function.h
+++ b/Phys/FunctorCore/include/Functors/Function.h
@@ -11,6 +11,8 @@
 #pragma once
 #include "Functors/Core.h"
 #include "Functors/Optional.h"
+#include "Functors/type_name.h"
+#include "Gaudi/Algorithm.h"
 #include "LHCbMath/MatVec.h"
 #include "SelKernel/Utilities.h"
 #include <cmath>
@@ -300,6 +302,28 @@ namespace Functors {
   constexpr auto Identity =
       TrivialFunctor{ "Identity", []<typename T>( T&& t ) -> decltype( auto ) { return std::forward<T>( t ); } };
 
+  /** @class Logger
+   *  @brief Trivial functor that prints the argument, and then returns it
+   */
+  class Logger : public Function {
+    std::string m_format;
+
+  public:
+    Logger( std::string format ) : m_format{ std::move( format ) } {}
+
+    auto prepare( EventContext const&, TopLevelInfo const& top_level ) const {
+      return [alg = top_level.algorithm(), format = std::string_view{ m_format }]<typename T>( T&& t ) -> T&& {
+        using GaudiUtils::operator<<;
+        std::stringstream s;
+        s << t;
+        alg->always() << fmt::format( fmt::runtime( format ), fmt::arg( "arg_type", type_name<T>() ),
+                                      fmt::arg( "arg", s.view() ) )
+                      << endmsg;
+        return std::forward<T>( t );
+      };
+    }
+  };
+
   /** @class Column
   Instantiated with a "label" , when acting on object T returns T("label")
    */
diff --git a/Phys/FunctorCore/include/Functors/type_name.h b/Phys/FunctorCore/include/Functors/type_name.h
new file mode 100644
index 0000000000000000000000000000000000000000..b46022056d226d662d5ca556f782f91dd09c55a5
--- /dev/null
+++ b/Phys/FunctorCore/include/Functors/type_name.h
@@ -0,0 +1,55 @@
+/*****************************************************************************\
+* (c) Copyright 2021, Matthew Rodusek (bitwizeshift)
+*
+* based on https://bitwizeshift.github.io/posts/2021/03/09/getting-an-unmangled-type-name-at-compile-time
+*
+\*****************************************************************************/
+#pragma once
+#include <array> // std::array
+#include <string>
+#include <string_view>
+#include <utility> // std::index_sequence
+
+namespace details {
+  template <std::size_t... Is>
+  constexpr auto as_array( std::string_view str, std::index_sequence<Is...> ) {
+    return std::array{ str[Is]... };
+  }
+
+  template <typename T>
+  constexpr auto type_name_array() {
+#if defined( __clang__ )
+    constexpr auto prefix   = std::string_view{ "[T = " };
+    constexpr auto suffix   = std::string_view{ "]" };
+    constexpr auto function = std::string_view{ __PRETTY_FUNCTION__ };
+#elif defined( __GNUC__ )
+    constexpr auto prefix   = std::string_view{ "with T = " };
+    constexpr auto suffix   = std::string_view{ "]" };
+    constexpr auto function = std::string_view{ __PRETTY_FUNCTION__ };
+#elif defined( _MSC_VER )
+    constexpr auto prefix   = std::string_view{ "type_name_array<" };
+    constexpr auto suffix   = std::string_view{ ">(void)" };
+    constexpr auto function = std::string_view{ __FUNCSIG__ };
+#else
+#  error Unsupported compiler
+#endif
+
+    constexpr auto start = function.find( prefix ) + prefix.size();
+    constexpr auto end   = function.rfind( suffix );
+    static_assert( start < end );
+
+    constexpr auto name = function.substr( start, ( end - start ) );
+    return as_array( name, std::make_index_sequence<name.size()>{} );
+  }
+
+  template <typename T>
+  struct type_name_holder {
+    static inline constexpr auto value = type_name_array<T>();
+  };
+} // namespace details
+
+template <typename T>
+constexpr std::string_view type_name() {
+  constexpr auto& value = details::type_name_holder<T>::value;
+  return std::string_view{ value.data(), value.size() };
+}
diff --git a/Phys/FunctorCore/python/Functors/__init__.py b/Phys/FunctorCore/python/Functors/__init__.py
index 95d7d5e04920634ac04c3ecbd848e4b8b24dcaa1..922b102bce3e40cb49e0de5c93704e1a7c3df606 100644
--- a/Phys/FunctorCore/python/Functors/__init__.py
+++ b/Phys/FunctorCore/python/Functors/__init__.py
@@ -1604,6 +1604,19 @@ PPHASMUONINFO = Functor(
 ALL = Functor("ALL", "AcceptAll", "Accept everything; always evaluates to 'true'.")
 NONE = Functor("NONE", "AcceptNone", "Accept nothing; always evaluates to 'false'.")
 IDENTITY = Functor("IDENTITY", "Identity", "Returns the same value.")
+LOGGER = Functor(
+    "LOGGER",
+    "Logger",
+    "Print argument, and then return the same value.",
+    Params=[
+        (
+            "Format",
+            "formatstring: use {arg} to specify the argument, and {arg_type} to print type of the argument",
+            str,
+        )
+    ],
+)
+
 COLUMN = Functor(
     "COLUMN",
     "Column_t",
diff --git a/Phys/FunctorCore/tests/options/test_functors_tested.py b/Phys/FunctorCore/tests/options/test_functors_tested.py
index f2a679f6115f262aa4f52bab9092a15591b036ab..eab163d681fa14b7a1b61b8fbb511d2ab6f11f04 100644
--- a/Phys/FunctorCore/tests/options/test_functors_tested.py
+++ b/Phys/FunctorCore/tests/options/test_functors_tested.py
@@ -61,6 +61,7 @@ exceptions = [
     "Functors::Common::Median",
     "Functors::Column_t",
     "Functors::Identity",
+    "Functors::Logger",
     "Functors::Particle::ParticlePropertyUser",
     "Functors::PID::RichThresholdDe",
     "Functors::PID::RichThresholdKa",