diff --git a/pyphare/pyphare/cpp/__init__.py b/pyphare/pyphare/cpp/__init__.py
index 79d0c8cf5..b42cb32c3 100644
--- a/pyphare/pyphare/cpp/__init__.py
+++ b/pyphare/pyphare/cpp/__init__.py
@@ -22,7 +22,7 @@ def cpp_lib(override=None):
         return importlib.import_module("pybindlibs.cpp")
     try:
         return importlib.import_module("pybindlibs.cpp_dbg")
-    except ImportError as err:
+    except ImportError:
         return importlib.import_module("pybindlibs.cpp")
 
 
@@ -36,6 +36,20 @@ def build_config():
     return cpp_etc_lib().phare_build_config()
 
 
+def env_vars():
+    return cpp_etc_lib().phare_env_vars()
+
+
+def print_env_vars_info():
+    # see: src/core/env.hpp
+    for env_var_name, env_var in cpp_etc_lib().phare_env_vars().items():
+        print(f"{env_var_name}: {env_var.desc}")
+        print("Options:")
+        for option_key, option_val in env_var.options:
+            print(f"  {option_key}: {option_val}")
+        print("")
+
+
 def build_config_as_json():
     return json.dumps(build_config())
 
diff --git a/res/cmake/test.cmake b/res/cmake/test.cmake
index 1f7331b1d..ea7355bd9 100644
--- a/res/cmake/test.cmake
+++ b/res/cmake/test.cmake
@@ -18,6 +18,7 @@ if (test AND ${PHARE_EXEC_LEVEL_MIN} GREATER 0) # 0 = no tests
   add_subdirectory(tests/core/data/maxwellian_particle_initializer)
   add_subdirectory(tests/core/data/particle_initializer)
   add_subdirectory(tests/core/utilities/box)
+  add_subdirectory(tests/core/utilities/env)
   add_subdirectory(tests/core/utilities/range)
   add_subdirectory(tests/core/utilities/index)
   add_subdirectory(tests/core/utilities/indexer)
diff --git a/src/core/env.hpp b/src/core/env.hpp
new file mode 100644
index 000000000..309f6b294
--- /dev/null
+++ b/src/core/env.hpp
@@ -0,0 +1,118 @@
+#ifndef PHARE_CORE_ENV_HPP
+#define PHARE_CORE_ENV_HPP
+
+// Single source for handling env vars
+
+#include <array>
+#include <cstdint>
+#include <optional>
+#include <string_view>
+#include <unordered_map>
+#include "core/utilities/types.hpp"
+#include "core/utilities/mpi_utils.hpp"
+
+namespace PHARE::env
+{
+
+struct Var
+{
+    using value_type                   = std::string;
+    using results_type                 = std::unordered_map<std::string, std::string>;
+    auto constexpr static noop_results = [](Var const&) { return results_type{}; };
+
+    std::string_view const id;
+    std::string_view const desc;
+    std::vector<std::pair<std::string_view, std::string_view>> const options;
+
+    std::optional<value_type> const _default               = std::nullopt;
+    std::function<results_type(Var const&)> const _results = noop_results;
+    std::optional<value_type> const v                      = get();
+    results_type const results                             = _results(*this);
+
+    std::optional<value_type> get() const
+    {
+        std::string _id{id};
+        if (_default)
+            return core::get_env(_id, *_default);
+        return core::get_env(_id);
+    }
+    auto const& operator()() const { return v; }
+    auto const& operator()(std::string const& s) const { return results.at(s); }
+    auto const& operator()(std::string const& s, std::string const& default_) const
+    {
+        if (results.count(s))
+            return results.at(s);
+        return default_;
+    }
+    bool exists() const { return v != std::nullopt; }
+    operator bool() const { return exists(); }
+};
+
+} // namespace PHARE::env
+
+namespace PHARE
+{
+class Env
+{
+public:
+    template<typename T>
+    using map_t = std::unordered_map<std::string, T const* const>;
+
+    static Env& INSTANCE()
+    {
+        if (!self)
+            self = std::make_unique<Env>();
+        return *self;
+    }
+    static auto& reinit() { return *(self = std::make_unique<Env>()); }
+
+    env::Var const PHARE_LOG{
+        "PHARE_LOG",
+        "Write logs to $CWD/.log",
+        {{{"RANK_FILES", "Write logs $CWD/.log, a file per rank"},
+          {"DATETIME_FILES", "Write logs $CWD/.log, filename per rank and datetime"},
+          {"NONE", "print normally to std::cout"}}},
+        std::nullopt,
+        [](auto const& self) {
+            std::string static const file_key = "PHARE_LOG_FILE";
+            typename env::Var::results_type map;
+            if (auto const& opt = self())
+            {
+                auto const& val = *opt;
+                if (val == "RANK_FILES")
+                    map[file_key] = ".log/" + std::to_string(core::mpi::rank()) + ".out";
+                else if (val == "DATETIME_FILES")
+                {
+                    auto date_time = core::mpi::date_time();
+                    auto rank      = std::to_string(core::mpi::rank());
+                    auto size      = std::to_string(core::mpi::size());
+                    map[file_key]  = ".log/" + date_time + "_" + rank + "_of_" + size + ".out";
+                }
+                else if (val != "NONE")
+                    throw std::runtime_error("PHARE_LOG invalid type, valid keys are "
+                                             "RANK_FILES/DATETIME_FILES/NONE");
+            }
+            return map;
+        } //
+    };
+    env::Var const PHARE_SCOPE_TIMING{
+        "PHARE_SCOPE_TIMING", "Enable function scope timing", {{{"1", "ON"}, {"0", "OFF"}}}, "0"};
+
+    map_t<env::Var> const vars = {{
+        {"PHARE_LOG", &PHARE_LOG},
+        {"PHARE_SCOPE_TIMING", &PHARE_SCOPE_TIMING},
+    }};
+
+    auto& operator()(std::string const& s) const
+    {
+        assert(vars.count(s));
+        return *vars.at(s);
+    }
+
+private:
+    static inline std::unique_ptr<Env> self = nullptr;
+};
+
+} // namespace PHARE
+
+#endif /* PHARE_CORE_ERRORS_H */
diff --git a/src/core/utilities/mpi_utils.cpp b/src/core/utilities/mpi_utils.cpp
index dae6f2b49..22b46b5cd 100644
--- a/src/core/utilities/mpi_utils.cpp
+++ b/src/core/utilities/mpi_utils.cpp
@@ -27,6 +27,7 @@ std::size_t max(std::size_t const local, int mpi_size)
 
 
 
+
 bool any(bool b)
 {
     int global_sum, local_sum = static_cast<int>(b);
diff --git a/src/core/utilities/mpi_utils.hpp b/src/core/utilities/mpi_utils.hpp
index 112c3f5a5..9897e0b23 100644
--- a/src/core/utilities/mpi_utils.hpp
+++ b/src/core/utilities/mpi_utils.hpp
@@ -40,6 +40,8 @@ inline bool is_init()
     return flag > 0;
 }
 
+
+
 template<typename Data>
 NO_DISCARD auto mpi_type_for()
 {
diff --git a/src/core/utilities/types.hpp b/src/core/utilities/types.hpp
index 412456da7..4ec11f7a4 100644
--- a/src/core/utilities/types.hpp
+++ b/src/core/utilities/types.hpp
@@ -195,6 +195,18 @@ namespace core
         T var;
     };
 
+    template<typename T>
+    NO_DISCARD T from_string(std::string const& s)
+    {
+        T t;
+        std::stringstream ss(s);
+        ss >> t;
+        ss >> t;
+        if (ss.fail())
+            throw std::runtime_error("PHARE::core::from_string - Conversion failed: " + s);
+        return t;
+    }
+
     template<typename T>
     NO_DISCARD std::string to_string_with_precision(T const& a_value, std::size_t const len)
     {
@@ -246,6 +258,24 @@ namespace core
     }
 
 
+    template<typename T>
+    NO_DISCARD inline std::optional<T> get_env_as(std::string const& key)
+    {
+        if (auto e = get_env(key))
+            return from_string<T>(*e);
+        return std::nullopt;
+    }
+
+
+    template<typename T>
+    NO_DISCARD inline T get_env_as(std::string const& key, T const& t)
+    {
+        if (auto e = get_env(key))
+            return from_string<T>(*e);
+        return t;
+    }
+
+
 
 } // namespace core
 } // namespace PHARE
diff --git a/src/hdf5/detail/h5/h5_file.hpp b/src/hdf5/detail/h5/h5_file.hpp
index 69980515c..18525e11c 100644
--- a/src/hdf5/detail/h5/h5_file.hpp
+++ b/src/hdf5/detail/h5/h5_file.hpp
@@ -69,7 +69,10 @@ class HighFiveFile
 
     ~HighFiveFile() {}
 
-    NO_DISCARD HiFile& file() { return h5file_; }
+    NO_DISCARD HiFile& file()
+    {
+        return h5file_;
+    }
 
 
     template<typename T, std::size_t dim = 1>
@@ -143,13 +146,11 @@ class HighFiveFile
     void write_attribute(std::string const& keyPath, std::string const& key, Data const& data)
     {
         // assumes all keyPaths and values are identical, and no null patches
-        // clang-format off
-        PHARE_DEBUG_DO(
+        PHARE_DEBUG_DO({
             auto const paths = core::mpi::collect(keyPath, core::mpi::size());
             if (!core::all(paths, [&](auto const& path) { return path == paths[0]; }))
                 throw std::runtime_error("Function does not support different paths per mpi core");
-        )
-        // clang-format on
+        })
 
         constexpr bool data_is_vector = core::is_std_vector_v<Data>;
 
diff --git a/src/phare/phare.hpp b/src/phare/phare.hpp
index d6519253f..e27c2a772 100644
--- a/src/phare/phare.hpp
+++ b/src/phare/phare.hpp
@@ -4,6 +4,8 @@
 
 #include "core/def/phlop.hpp" // scope timing
 
+#include "core/env.hpp" // scope timing
+
 #include "simulator/simulator.hpp"
 #include "core/utilities/algorithm.hpp"
 #include "core/utilities/mpi_utils.hpp"
@@ -41,7 +43,7 @@ class SamraiLifeCycle
             = std::make_shared<StreamAppender>(StreamAppender{&std::cout});
         SAMRAI::tbox::Logger::getInstance()->setWarningAppender(appender);
         PHARE_WITH_PHLOP( //
-            if (auto e = core::get_env("PHARE_SCOPE_TIMING", "false"); e == "1" || e == "true")
+            if (auto e = Env::INSTANCE().PHARE_SCOPE_TIMING(); e == "1" || e == "true")
                 phlop::ScopeTimerMan::INSTANCE()
                     .file_name(".phare_times." + std::to_string(core::mpi::rank()) + ".txt")
                     .init(); //
diff --git a/src/python3/cpp_etc.cpp b/src/python3/cpp_etc.cpp
index 0550c5a0a..8afe08877 100644
--- a/src/python3/cpp_etc.cpp
+++ b/src/python3/cpp_etc.cpp
@@ -1,16 +1,18 @@
 
+#include "pybind11/stl.h"
+#include "pybind11/stl_bind.h"
 #include "python3/pybind_def.hpp"
 #include "simulator/simulator.hpp"
 
+#include "core/env.hpp"
 #include "core/def/phare_config.hpp"
 
-
 #include "amr/wrappers/hierarchy.hpp" // for HierarchyRestarter::getRestartFileFullPath
 
-
-
 namespace py = pybind11;
 
+PYBIND11_MAKE_OPAQUE(std::unordered_map<std::string, PHARE::env::Var*>);
+
 namespace PHARE::pydata
 {
 auto pybind_version()
@@ -55,5 +57,21 @@ PYBIND11_MODULE(cpp_etc, m)
     });
 
     m.def("phare_build_config", []() { return PHARE::build_config(); });
+
+    m.def("phare_env_exists",
+          [](std::string const& s) { return Env::INSTANCE().vars.count(s) > 0; });
+    m.def("phare_env_val", [](std::string const& s) { return Env::INSTANCE()(s)(); });
+    py::class_<env::Var>(m, "phare_env_var")
+        .def_readonly("id", &env::Var::id)
+        .def_readonly("desc", &env::Var::desc)
+        .def_readonly("options", &env::Var::options)
+        .def_readonly("default", &env::Var::_default)
+        .def_readonly("results", &env::Var::results);
+
+    py::bind_map<std::unordered_map<std::string, env::Var*>>(m, "EnvVarMap");
+
+    m.def(
+        "phare_env_vars", []() -> auto& { return Env::INSTANCE().vars; },
+        py::return_value_policy::reference);
 }
 } // namespace PHARE::pydata
diff --git a/src/simulator/simulator.hpp b/src/simulator/simulator.hpp
index 84561ce27..7db37710a 100644
--- a/src/simulator/simulator.hpp
+++ b/src/simulator/simulator.hpp
@@ -8,6 +8,7 @@
 #include "phare_types.hpp"
 
 #include "core/def.hpp"
+#include "core/env.hpp"
 #include "core/logger.hpp"
 #include "core/utilities/types.hpp"
 #include "core/utilities/mpi_utils.hpp"
@@ -116,32 +117,7 @@ class Simulator : public ISimulator
 private:
     auto find_model(std::string name);
 
-    auto static log_file_name()
-    {
-        // ".log" directory is not created here, but in python if PHARE_LOG != "NONE"
-        if (auto log = core::get_env("PHARE_LOG"))
-        {
-            if (log == "RANK_FILES")
-                return ".log/" + std::to_string(core::mpi::rank()) + ".out";
-
-
-            if (log == "DATETIME_FILES")
-            {
-                auto date_time = core::mpi::date_time();
-                auto rank      = std::to_string(core::mpi::rank());
-                auto size      = std::to_string(core::mpi::size());
-                return ".log/" + date_time + "_" + rank + "_of_" + size + ".out";
-            }
-
-            if (log != "NONE")
-                throw std::runtime_error(
-                    "PHARE_LOG invalid type, valid keys are RANK_FILES/DATETIME_FILES/NONE");
-        }
-
-        return std::string{""}; // unused
-    }
-
-    std::ofstream log_out{log_file_name()};
+    std::ofstream log_out{Env::INSTANCE().PHARE_LOG("PHARE_LOG_FILE", "")};
     std::streambuf* coutbuf = nullptr;
     std::shared_ptr<PHARE::amr::Hierarchy> hierarchy_;
     std::unique_ptr<Integrator> integrator_;
@@ -192,7 +168,7 @@ namespace
     inline auto logging(std::ofstream& log_out)
     {
         std::streambuf* buf = nullptr;
-        if (auto log = core::get_env("PHARE_LOG"); log != "NONE")
+        if (auto log = Env::INSTANCE().PHARE_LOG(); log and log != "NONE")
         {
             buf = std::cout.rdbuf();
             std::cout.rdbuf(log_out.rdbuf());
diff --git a/tests/core/utilities/env/CMakeLists.txt b/tests/core/utilities/env/CMakeLists.txt
new file mode 100644
index 000000000..ef9ac396f
--- /dev/null
+++ b/tests/core/utilities/env/CMakeLists.txt
@@ -0,0 +1,21 @@
+cmake_minimum_required (VERSION 3.20.1)
+
+project(test-phare-env)
+
+set(SOURCES test_env.cpp)
+
+add_executable(${PROJECT_NAME} ${SOURCES})
+
+target_include_directories(${PROJECT_NAME} PRIVATE
+  ${GTEST_INCLUDE_DIRS}
+  )
+
+target_link_directories(${PROJECT_NAME} PUBLIC ${MPI_LIBRARY_PATH})
+
+target_link_libraries(${PROJECT_NAME} PRIVATE
+  phare_core
+  MPI::MPI_C
+  ${GTEST_LIBS}
+)
+
+add_phare_test(${PROJECT_NAME} ${CMAKE_CURRENT_BINARY_DIR})
diff --git a/tests/core/utilities/env/test_env.cpp b/tests/core/utilities/env/test_env.cpp
new file mode 100644
index 000000000..291ade050
--- /dev/null
+++ b/tests/core/utilities/env/test_env.cpp
@@ -0,0 +1,43 @@
+
+
+#include "core/env.hpp"
+#include "tests/core/utilities/test_mpi_utils.hpp"
+
+#include "gtest/gtest.h"
+#include <cstdlib>
+
+namespace PHARE
+{
+
+TEST(Env, env_setting_works)
+{
+    {
+        auto& env = Env::reinit(); // init
+
+        EXPECT_EQ(env.PHARE_LOG(), std::nullopt);
+    }
+
+    setenv("PHARE_LOG", "NONE", true);
+    auto& env = Env::reinit(); // init
+
+    EXPECT_EQ(env.PHARE_LOG(), "NONE");
+    EXPECT_EQ(env.PHARE_SCOPE_TIMING(), "0"); // default
+}
+
+
+TEST(Env, logging_works_rank_files)
+{
+    setenv("PHARE_LOG", "RANK_FILES", true);
+    auto& env = Env::reinit(); // init
+    EXPECT_EQ(env.PHARE_LOG("PHARE_LOG_FILE"),
+              ".log/" + std::to_string(core::mpi::rank()) + ".out");
+}
+
+} // namespace PHARE
+
+int main(int argc, char** argv)
+{
+    ::testing::InitGoogleTest(&argc, argv);
+    PHARE::core::mpi::Lifecycle mpi_init(argc, argv);
+    return RUN_ALL_TESTS();
+}
diff --git a/tests/core/utilities/test_mpi_utils.hpp b/tests/core/utilities/test_mpi_utils.hpp
new file mode 100644
index 000000000..72cc50213
--- /dev/null
+++ b/tests/core/utilities/test_mpi_utils.hpp
@@ -0,0 +1,40 @@
+#ifndef PHARE_TEST_CORE_UTILITIES_MPI_HPP
+#define PHARE_TEST_CORE_UTILITIES_MPI_HPP
+
+#include "core/utilities/mpi_utils.hpp"
+#include <iostream>
+
+namespace PHARE::core::mpi
+{
+
+
+struct Lifecycle
+{
+    static inline bool error_occurred = false;
+
+    Lifecycle(int argc, char** argv)
+    {
+        int err = MPI_Init(&argc, &argv);
+        if (err != MPI_SUCCESS)
+        {
+            std::cerr << "MPI Initialization failed with error code: " << err << std::endl;
+            error_occurred = true;
+        }
+    }
+    ~Lifecycle()
+    {
+        if (!error_occurred)
+        {
+            int err = MPI_Finalize();
+            if (err != MPI_SUCCESS)
+            {
+                std::cerr << "MPI Finalization failed with error code: " << err << std::endl;
+            }
+        }
+    }
+};
+
+} // namespace PHARE::core::mpi
+
+
+#endif /* PHARE_TEST_CORE_UTILITIES_MPI_H */