diff --git a/src/beast/SConstruct b/src/beast/SConstruct
index 4ace976a43..1513509394 100644
--- a/src/beast/SConstruct
+++ b/src/beast/SConstruct
@@ -1,160 +1,48 @@
-# Beast scons file
-#
-#-------------------------------------------------------------------------------
+from __future__ import absolute_import, division, print_function, unicode_literals
 
-import ntpath
+import copy
 import os
 import sys
-import textwrap
-#import re
-#import json
-#import urlparse
-#import posixpath
-#import string
-#import subprocess
-#import platform
-#import itertools
 
-#-------------------------------------------------------------------------------
+def add_beast_to_path():
+    python_home = os.path.join(os.getcwd(), 'python')
+    if python_home not in sys.path:
+        sys.path.append(python_home)
 
-# Format a name value pair
-def print_nv_pair(n, v):
-    name = ("%s" % n.rjust(10))
-    sys.stdout.write("%s \033[94m%s\033[0m\n" % (name, v))
+add_beast_to_path()
 
-# Pretty-print values as a build configuration
-def print_build_vars(env,var):
-    val = env.get(var, '')
+from beast.env.AddCommonFlags import add_common_flags
+from beast.env.AddUserEnv import add_user_env
+from beast.env import Print
+from beast.platform import GetEnvironment
+from beast.util import Boost
+from beast.util import File
+from beast.util import Tests
 
-    if val and val != '':
-        name = ("%s" % var.rjust(10))
+VARIANT_DIRECTORIES = {
+    'beast': ('bin', 'beast'),
+    'modules': ('bin', 'modules'),
+}
 
-        wrapper = textwrap.TextWrapper()
-        wrapper.break_long_words = False
-        wrapper.break_on_hyphens = False
-        wrapper.width = 69
-
-        if type(val) is str:
-            lines = wrapper.wrap(val)
-        else:
-            lines = wrapper.wrap(" ".join(str(x) for x in val))
-
-        for line in lines:
-            print_nv_pair (name, line)
-            name = "          "
-
-def print_build_config(env):
-    config_vars = ['CC', 'CXX', 'CFLAGS', 'CCFLAGS', 'CPPFLAGS',
-                   'CXXFLAGS', 'LIBPATH', 'LINKFLAGS', 'LIBS', 'BOOST_HOME']
-    sys.stdout.write("\nConfiguration:\n")
-    for var in config_vars:
-        print_build_vars(env,var)
-    print
-
-def print_cmd_line(s, target, src, env):
-    target = (''.join([str(x) for x in target]))
-    source = (''.join([str(x) for x in src]))
-    name = target
-    print '           \033[94m' + name + '\033[0m'
-
-#-------------------------------------------------------------------------------
-
-# Returns the list of libraries needed by the test source file. This is
-# accomplished by scanning the source file for a special comment line
-# with this format, which must match exactly:
-#
-# // LIBS: <name>...
-#
-# path = path to source file
-#
-def get_libs(path):
-    prefix = '// LIBS:'
-    with open(path, 'rb') as f:
-        for line in f:
-            line = line.strip()
-            if line.startswith(prefix):
-                items = line.split(prefix, 1)[1].strip()
-                return [x.strip() for x in items.split(' ')]
-
-# Returns the list of source modules needed by the test source file. This
-#
-# // MODULES: <module>...
-#
-# path = path to source file
-#
-def get_mods(path):
-    prefix = '// MODULES:'
-    with open(path, 'rb') as f:
-        for line in f:
-            line = line.strip()
-            if line.startswith(prefix):
-                items = line.split(prefix, 1)[1].strip()
-                items = [os.path.normpath(os.path.join(
-                    os.path.dirname(path), x.strip())) for
-                        x in items.split(' ')]
-                return items
-
-# Build a stand alone executable that runs
-# all the test suites in one source file
-#
-def build_test(env,path):
-    libs = get_libs(path)
-    mods = get_mods(path)
-    bin = os.path.basename(os.path.splitext(path)[0])
-    bin = os.path.join ("bin", bin)
-    srcs = ['beast/unit_test/tests/main.cpp']
-    srcs.append (path)
-    if mods:
-        srcs.extend (mods)
-    # All paths get normalized here, so we can use posix
-    # forward slashes for everything including on Windows
-    srcs = [os.path.normpath(os.path.join ('bin', x)) for x in srcs]
-    objs = [os.path.splitext(x)[0]+'.o' for x in srcs]
-    env_ = env
-    if libs:
-        env_.Append(LIBS = libs)
-    env_.Program (bin, srcs)
-
-#-------------------------------------------------------------------------------
+BOOST_LIBRARIES = 'boost_system',
+MAIN_PROGRAM_FILE = 'beast/unit_test/tests/main.cpp'
+DOTFILE = '~/.scons'
 
 def main():
-    env = Environment()
+    File.validate_libraries(Boost.LIBPATH, BOOST_LIBRARIES)
+    defaults = GetEnvironment.get_environment(ARGUMENTS)
+    working = copy.deepcopy(defaults)
+    add_common_flags(defaults)
 
-    env['PRINT_CMD_LINE_FUNC'] = print_cmd_line
+    add_user_env(working, DOTFILE)
+    add_common_flags(working)
+    Print.print_build_config(working, defaults)
 
-    env.VariantDir (os.path.join ('bin', 'beast'), 'beast', duplicate=0)
-    env.VariantDir (os.path.join ('bin', 'modules'), 'modules', duplicate=0)
+    env = Environment(**working)
 
-    # Copy important os environment variables into env
-    if os.environ.get ('CC', None):
-        env.Replace (CC = os.environ['CC'])
-    if os.environ.get ('CXX', None):
-        env.Replace (CXX = os.environ['CXX'])
-    if os.environ.get ('PATH', None):
-        env.Replace (PATH = os.environ['PATH'])
-
-    # Set up boost variables
-    home = os.environ.get("BOOST_HOME", None)
-    if home is not None:
-        env.Prepend (CPPPATH = home)
-        env.Append (LIBPATH = os.path.join (home, 'stage', 'lib'))
-
-    # Set up flags
-    env.Append(CXXFLAGS = [
-        '-std=c++11',
-        '-frtti',
-        '-O3',
-        '-fno-strict-aliasing',
-        '-g'
-        ])
-
-    for root, dirs, files in os.walk('.'):
-        for path in files:
-            path = os.path.join(root,path)
-            if (path.endswith(".test.cpp")):
-                build_test(env,path)
-
-    print_build_config (env)
+    for name, path in VARIANT_DIRECTORIES.items():
+        env.VariantDir(os.path.join(*path), name, duplicate=0)
+    env.Replace(PRINT_CMD_LINE_FUNC=Print.print_cmd_line)
+    Tests.run_tests(env, MAIN_PROGRAM_FILE, '.', '.test.cpp')
 
 main()
-
diff --git a/src/beast/beast/chrono/basic_seconds_clock.h b/src/beast/beast/chrono/basic_seconds_clock.h
index 2e15fdcc42..42db9ab95a 100644
--- a/src/beast/beast/chrono/basic_seconds_clock.h
+++ b/src/beast/beast/chrono/basic_seconds_clock.h
@@ -22,6 +22,7 @@
 
 #include <algorithm>
 #include <chrono>
+#include <vector>
 
 #ifndef BEAST_BASIC_SECONDS_CLOCK_BOOST_WORKAROUND
 # ifdef _MSC_VER
diff --git a/src/beast/beast/config/PlatformConfig.h b/src/beast/beast/config/PlatformConfig.h
index 5e94998da3..12af9c889c 100644
--- a/src/beast/beast/config/PlatformConfig.h
+++ b/src/beast/beast/config/PlatformConfig.h
@@ -101,10 +101,6 @@
     #define BEAST_DEBUG 1
   #endif
 
-  #if ! (defined (DEBUG) || defined (_DEBUG) || defined (NDEBUG) || defined (_NDEBUG))
-//    #warning "Neither NDEBUG or DEBUG has been defined - you should set one of these to make it clear whether this is a release build,"
-  #endif
-
   #ifdef __LITTLE_ENDIAN__
     #define BEAST_LITTLE_ENDIAN 1
   #else
@@ -213,4 +209,3 @@
 #define BEAST_FILEANDLINE_ __FILE__ "(" BEAST_PP_STR1_(__LINE__) "): warning:"
 
 #endif
-
diff --git a/src/beast/python/README b/src/beast/python/README
new file mode 100644
index 0000000000..494b1cb07d
--- /dev/null
+++ b/src/beast/python/README
@@ -0,0 +1,10 @@
+Python code for the beast and scons.
+
+Scripts you can run from this directory.
+
+./run-tests.sh
+  Runs the unit tests.
+
+./clean-python.sh
+  If you remove or rename any Python files, you should run this script to
+  prevent old .pyc files from hiding bugs.
\ No newline at end of file
diff --git a/src/beast/python/beast/__init__.py b/src/beast/python/beast/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/src/beast/python/beast/env/AddCommonFlags.py b/src/beast/python/beast/env/AddCommonFlags.py
new file mode 100644
index 0000000000..d541262a62
--- /dev/null
+++ b/src/beast/python/beast/env/AddCommonFlags.py
@@ -0,0 +1,11 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from beast.util import Boost
+from beast.util import Git
+
+def add_common_flags(env):
+    git_flag = '-DTIP_BRANCH="%s"' % Git.describe()
+    env['CPPFLAGS'] = '%s %s' % (env['CPPFLAGS'], git_flag)
+    env['CPPPATH'].insert(0, Boost.CPPPATH)
+    env['LIBPATH'].append(Boost.LIBPATH)
+    env['BOOST_HOME'] = Boost.CPPPATH
diff --git a/src/beast/python/beast/env/AddUserEnv.py b/src/beast/python/beast/env/AddUserEnv.py
new file mode 100644
index 0000000000..8d5056a708
--- /dev/null
+++ b/src/beast/python/beast/env/AddUserEnv.py
@@ -0,0 +1,38 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import os
+import shlex
+
+from beast.env.ReadEnvFile import read_env_file
+from beast.util.String import is_string
+from beast.util.Terminal import warn
+
+_BAD_VARS_ERROR = """
+the following variables appearing in %s were not understood:
+  %s"""
+
+def add_user_env(env, dotfile, print=print):
+    df = os.path.expanduser(dotfile)
+    try:
+        with open(df, 'r') as f:
+            dotvars = read_env_file(f.read())
+    except IOError:
+        if os.path.exists(df):
+            warn("Dotfile %s exists but can't be read." % dotfile, print)
+        dotvars = {}
+
+    bad_names = []
+    for name, value in dotvars.items():
+        if name in env:
+            if is_string(env[name]):
+                env[name] = value
+            else:
+                env[name] = shlex.split(value)
+        else:
+            bad_names.append(name)
+    if bad_names:
+        error = _BAD_VARS_ERROR % (dotfile, '\n  '.join(bad_names))
+        warn(error, print)
+
+    for name, default in env.items():
+        env[name] = os.environ.get(name, default)
diff --git a/src/beast/python/beast/env/Print.py b/src/beast/python/beast/env/Print.py
new file mode 100644
index 0000000000..163b73bfab
--- /dev/null
+++ b/src/beast/python/beast/env/Print.py
@@ -0,0 +1,41 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import textwrap
+
+from beast.util import String
+from beast.util import Terminal
+
+FIELD_WIDTH = 10
+LINE_WIDTH = 69
+
+EMPTY_NAME = ' ' * FIELD_WIDTH
+
+TEXT_WRAPPER = textwrap.TextWrapper(
+    break_long_words=False,
+    break_on_hyphens=False,
+    width=LINE_WIDTH,
+)
+
+DISPLAY_EMPTY_ENVS = True
+
+def print_build_vars(name, value, same, print=print):
+    """Pretty-print values as a build configuration."""
+    name = '%s' % name.rjust(FIELD_WIDTH)
+    color = Terminal.blue if same else Terminal.green
+
+    for line in TEXT_WRAPPER.wrap(String.stringify(value, ' ')):
+        print(' '.join([name, color(line)]))
+        name = EMPTY_NAME
+
+def print_cmd_line(s, target, source, env):
+    print(EMPTY_NAME + Terminal.blue(String.stringify(target)))
+
+def print_build_config(env, original, print=print):
+    print('\nConfiguration:')
+    for name, value in env.items():
+        if value or DISPLAY_EMPTY_ENVS:
+            same = (value == original[name])
+            if not same:
+                print('"%s" != "%s"' % (value, original[name]))
+            print_build_vars(name, value, same, print=print)
+    print()
diff --git a/src/beast/python/beast/env/ReadEnvFile.py b/src/beast/python/beast/env/ReadEnvFile.py
new file mode 100644
index 0000000000..fce83e2172
--- /dev/null
+++ b/src/beast/python/beast/env/ReadEnvFile.py
@@ -0,0 +1,34 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import json
+import re
+
+from beast.util import String
+from beast.util.Terminal import warn
+
+ENV_LINE_MATCH = re.compile(r'(?: export \s+)? \s* ([^=\s]*) \s* = (.*)',
+                            re.VERBOSE)
+
+def read_env_file(data, print=print):
+    try:
+        return json.loads(data)
+    except ValueError:
+        pass
+
+    bad_lines = []
+    results = {}
+    for number, raw_line in enumerate(data.splitlines()):
+        line = String.remove_comment(raw_line).strip()
+        if line:
+            match = ENV_LINE_MATCH.match(line)
+            if match:
+                name, value = match.groups()
+                results[name.strip()] = String.remove_quotes(value.strip())
+            else:
+                bad_lines.append([number, raw_line])
+    if bad_lines:
+         warn("Didn't understand the following environment file lines:", print)
+         for number, line in bad_lines:
+             print('%d. >>> %s' % (number + 1, line))
+
+    return results
diff --git a/src/beast/python/beast/env/ReadEnvFile_test.py b/src/beast/python/beast/env/ReadEnvFile_test.py
new file mode 100644
index 0000000000..7c419b5717
--- /dev/null
+++ b/src/beast/python/beast/env/ReadEnvFile_test.py
@@ -0,0 +1,51 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from unittest import TestCase
+from beast.env.ReadEnvFile import read_env_file
+
+from beast.util import Terminal
+Terminal.CAN_CHANGE_COLOR = False
+
+JSON = """
+{
+  "FOO": "foo",
+  "BAR": "bar bar bar",
+  "CPPFLAGS": "-std=c++11 -frtti -fno-strict-aliasing -DWOMBAT"
+}"""
+
+ENV = """
+# An env file.
+
+FOO=foo
+export BAR="bar bar bar"
+CPPFLAGS=-std=c++11 -frtti -fno-strict-aliasing -DWOMBAT
+
+# export BAZ=baz should be ignored.
+
+"""
+
+RESULT = {
+    'FOO': 'foo',
+    'BAR': 'bar bar bar',
+    'CPPFLAGS': '-std=c++11 -frtti -fno-strict-aliasing -DWOMBAT',
+    }
+
+BAD_ENV = ENV + """
+This line isn't right.
+NO SPACES IN NAMES="valid value"
+"""
+
+class test_ReadEnvFile(TestCase):
+  def test_read_json(self):
+    self.assertEqual(read_env_file(JSON), RESULT)
+
+  def test_read_env(self):
+    self.assertEqual(read_env_file(ENV), RESULT)
+
+  def test_read_env_error(self):
+    errors = []
+    self.assertEqual(read_env_file(BAD_ENV, errors.append), RESULT)
+    self.assertEqual(errors, [
+        "WARNING: Didn't understand the following environment file lines:",
+        "11. >>> This line isn't right.",
+        '12. >>> NO SPACES IN NAMES="valid value"'])
diff --git a/src/beast/python/beast/env/Tags.py b/src/beast/python/beast/env/Tags.py
new file mode 100644
index 0000000000..6bd0861e75
--- /dev/null
+++ b/src/beast/python/beast/env/Tags.py
@@ -0,0 +1,17 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from beast.util.Terminal import warn
+
+_TAGS = frozenset(['debug', 'optimize'])
+
+def _to_tag(name, value):
+    return '%s%s' % ('' if value else 'no', name)
+
+def get_tags(arguments, print=print):
+    result = {}
+    bad_tags = set(arguments) - _TAGS
+    if bad_tags:
+        warn("don't understand tags " + ' '.join(bad_tags), print=print)
+    debug = result.get('debug', True)
+    optimize = result.get('optimize', not debug)
+    return _to_tag('debug', debug), _to_tag('optimize', optimize)
diff --git a/src/beast/python/beast/env/__init__.py b/src/beast/python/beast/env/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/src/beast/python/beast/platform/GetEnvironment.py b/src/beast/python/beast/platform/GetEnvironment.py
new file mode 100644
index 0000000000..89b14f1964
--- /dev/null
+++ b/src/beast/python/beast/platform/GetEnvironment.py
@@ -0,0 +1,59 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from beast.platform import Platform
+from beast.util import Dict
+from beast.env import Tags
+
+_DEFAULTS = {
+    '': {
+        'BOOST_HOME': None,
+        'CC': 'gcc',
+        'CCFLAGS': None,
+        'CFLAGS': None,
+        'CXX': 'g++',
+        'CPPFLAGS': '-std=c++11 -frtti -fno-strict-aliasing',
+        'CPPPATH': [],
+        'LIBPATH': [],
+        'LIBS': [],
+        'LINKFLAGS': '',
+    },
+
+    'Darwin': {
+        'CC': 'clang',
+        'CXX': 'clang++',
+        'CPPFLAGS': '-x c++ -stdlib=libc++ -std=c++11 -frtti',
+        'LINKFLAGS': '-stdlib=libc++',
+     },
+
+    'FreeBSD': {
+        'CC': 'gcc46',
+        'CXX': 'g++46',
+        'CCFLAGS': '-Wl,-rpath=/usr/local/lib/gcc46',
+        'LINKFLAGS': '-Wl,-rpath=/usr/local/lib/gcc46',
+        'LIBS': ['kvm'],
+    },
+
+    # TODO: specific flags for Windows, Linux platforms.
+}
+
+TAGS = {
+    'debug': {
+        'CPPFLAGS': '-g -DDEBUG'
+        },
+
+    'optimize': {
+        'CPPFLAGS': '-O3',
+        },
+
+    'nooptimize': {
+        'CPPFLAGS': '-O0',
+        }
+    }
+
+def get_environment(arguments):
+    tags = Tags.get_tags(arguments)
+    env = Dict.compose_prefix_dicts(Platform.PLATFORM, _DEFAULTS)
+    for tag in tags or []:
+        for k, v in TAGS.get(tag, {}).items():
+            env[k] = '%s %s' % (env[k], v)
+    return env
diff --git a/src/beast/python/beast/platform/Platform.py b/src/beast/python/beast/platform/Platform.py
new file mode 100644
index 0000000000..1b16e9f6ac
--- /dev/null
+++ b/src/beast/python/beast/platform/Platform.py
@@ -0,0 +1,27 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import platform
+
+def _get_platform_string():
+    system = platform.system()
+    parts = [system]
+    linux = system == 'Linux'
+    if linux:
+        flavor, version, _ = platform.linux_distribution()
+        # Arch still has issues with the platform module
+        parts[0] = flavor.capitalize() or 'Archlinux'
+        parts.extend(version.split('.'))
+    elif system == 'Darwin':
+        ten, major, minor = platform.mac_ver()[0].split('.')
+        parts.extend([ten, major, minor])
+    elif system == 'Windows':
+        release, version, csd, ptype = platform.win32_ver()
+        parts.extend([release, version, csd, ptype])
+    elif system == 'FreeBSD':
+        # No other variables to pass with FreeBSD that Python provides and I could find
+        pass
+    else:
+        raise Exception("Don't understand how to build for platform " + system)
+    return '.'.join(parts), linux
+
+PLATFORM, IS_LINUX = _get_platform_string()
diff --git a/src/beast/python/beast/platform/__init__.py b/src/beast/python/beast/platform/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/src/beast/python/beast/util/Boost.py b/src/beast/python/beast/util/Boost.py
new file mode 100644
index 0000000000..d7faf17af7
--- /dev/null
+++ b/src/beast/python/beast/util/Boost.py
@@ -0,0 +1,61 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import os
+import re
+
+ROOT_ENV_VARIABLE = 'BOOST_ROOT'
+MINIMUM_VERSION = 1, 55, 0
+VERSION_FILE = 'boost', 'version.hpp'
+LIBRARY_PATH_SEGMENT = 'stage', 'lib'
+VERSION_MATCHER = re.compile(r'#define\s+BOOST_VERSION\s+(\d+)')
+
+CANT_OPEN_VERSION_FILE_ERROR = """Unable to open boost version file %s.
+You have set the environment variable BOOST_ROOT to be %s.
+Please check to make sure that this points to a valid installation of boost."""
+
+CANT_UNDERSTAND_VERSION_ERROR = (
+    "Didn't understand version string '%s' from file %s'")
+VERSION_TOO_OLD_ERROR = ('Your version of boost, %s, is older than the minimum '
+                         'required, %s.')
+
+def _text(major, minor, release):
+    return '%d.%02d.%02d' % (major, minor, release)
+
+def _raw_boost_path():
+    try:
+      path = os.environ[ROOT_ENV_VARIABLE]
+      if path:
+        return os.path.normpath(path)
+    except KeyError:
+        pass
+    raise KeyError('%s environment variable is not set.' % ROOT_ENV_VARIABLE)
+
+def _get_version_number(path):
+    version_file = os.path.join(path, *VERSION_FILE)
+    try:
+        with open(version_file) as f:
+            for line in f:
+                match = VERSION_MATCHER.match(line)
+                if match:
+                    version = match.group(1)
+                    try:
+                        return int(version)
+                    except ValueError:
+                        raise Exception(CANT_UNDERSTAND_VERSION_ERROR %
+                                        (version, version_file))
+    except IOError:
+        raise Exception(CANT_OPEN_VERSION_FILE_ERROR % (version_file, path))
+
+def _validate_version(v):
+    version = v // 100000, (v // 100) % 100, v % 100
+    if version < MINIMUM_VERSION:
+        raise Exception(VERSION_TOO_OLD_ERROR % (
+    _text(*version), _text(*MINIMUM_VERSION)))
+
+def _boost_path():
+    path = _raw_boost_path()
+    _validate_version(_get_version_number(path))
+    return path
+
+CPPPATH = _boost_path()
+LIBPATH = os.path.join(CPPPATH, *LIBRARY_PATH_SEGMENT)
diff --git a/src/beast/python/beast/util/Dict.py b/src/beast/python/beast/util/Dict.py
new file mode 100644
index 0000000000..67ee13369c
--- /dev/null
+++ b/src/beast/python/beast/util/Dict.py
@@ -0,0 +1,17 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+def compose(*dicts):
+    result = {}
+    for d in dicts:
+        result.update(**d)
+    return result
+
+def get_items_with_prefix(key, mapping):
+    """Get all elements from the mapping whose keys are a prefix of the given
+    key, sorted by increasing key length."""
+    for k, v in sorted(mapping.items()):
+        if key.startswith(k):
+            yield v
+
+def compose_prefix_dicts(key, mapping):
+    return compose(*get_items_with_prefix(key, mapping))
diff --git a/src/beast/python/beast/util/Dict_test.py b/src/beast/python/beast/util/Dict_test.py
new file mode 100644
index 0000000000..690921e229
--- /dev/null
+++ b/src/beast/python/beast/util/Dict_test.py
@@ -0,0 +1,56 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from unittest import TestCase
+
+from beast.util import Dict
+
+DICT = {
+    '': {
+        'foo': 'foo-default',
+        'bar': 'bar-default',
+      },
+
+    'Darwin': {
+        'foo': 'foo-darwin',
+        'baz': 'baz-darwin',
+      },
+
+    'Darwin.10.8': {
+        'foo': 'foo-darwin-10.8',
+        'bing': 'bing-darwin-10.8',
+      },
+  }
+
+class test_Dict(TestCase):
+    def computeMapValue(self, config, key):
+        return Dict.compose(*Dict.get_items_with_prefix(config, DICT))[key]
+
+    def assertMapValue(self, config, key, result):
+        self.assertEquals(self.computeMapValue(config, key), result)
+
+    def testDefault1(self):
+        self.assertMapValue('', 'foo', 'foo-default')
+
+    def testDefault2(self):
+        self.assertMapValue('Darwin.10.8', 'bar', 'bar-default')
+
+    def testPrefix1(self):
+        self.assertMapValue('Darwin', 'foo', 'foo-darwin')
+
+    def testPrefix2(self):
+        self.assertMapValue('Darwin.10.8', 'foo', 'foo-darwin-10.8')
+
+    def testPrefix3(self):
+        self.assertMapValue('Darwin', 'baz', 'baz-darwin')
+
+    def testPrefix4(self):
+        self.assertMapValue('Darwin.10.8', 'bing', 'bing-darwin-10.8')
+
+    def testFailure1(self):
+        self.assertRaises(KeyError, self.computeMapValue, '', 'baz')
+
+    def testFailure2(self):
+        self.assertRaises(KeyError, self.computeMapValue, '', 'bing')
+
+    def testFailure2(self):
+        self.assertRaises(KeyError, self.computeMapValue, 'Darwin', 'bing')
diff --git a/src/beast/python/beast/util/Execute.py b/src/beast/python/beast/util/Execute.py
new file mode 100644
index 0000000000..65c6adfd1b
--- /dev/null
+++ b/src/beast/python/beast/util/Execute.py
@@ -0,0 +1,14 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import subprocess
+
+from beast.util import String
+
+def execute(args, include_errors=True, **kwds):
+    """Execute a shell command and return the value.  If args is a string,
+    it's split on spaces - if some of your arguments contain spaces, args should
+    instead be a list of arguments."""
+    if String.is_string(args):
+        args = args.split()
+    stderr = subprocess.STDOUT if include_errors else None
+    return subprocess.check_output(args, stderr=stderr, **kwds)
diff --git a/src/beast/python/beast/util/File.py b/src/beast/python/beast/util/File.py
new file mode 100644
index 0000000000..b8c99f54b0
--- /dev/null
+++ b/src/beast/python/beast/util/File.py
@@ -0,0 +1,42 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from beast.util import String
+
+import os
+
+LIBRARY_PATTERNS = 'lib%s.a', 'lib%s.dylib'
+
+def first_fields_after_prefix(filename, prefix):
+    with open(filename, 'r') as f:
+        return String.first_fields_after_prefix(prefix, f)
+
+def find_files_with_suffix(base, suffix):
+    for parent, _, files in os.walk(base):
+        for path in files:
+            path = os.path.join(parent, path)
+            if path.endswith(suffix):
+                yield os.path.normpath(path)
+
+def child_files(parent, files):
+    return [os.path.normpath(os.path.join(parent, f)) for f in files]
+
+def sibling_files(path, files):
+    return child_files(os.path.dirname(path), files)
+
+def replace_extension(file, ext):
+    return os.path.splitext(file)[0] + ext
+
+def validate_libraries(path, libraries):
+    bad = []
+    for lib in libraries:
+        found = False
+        for pat in LIBRARY_PATTERNS:
+            libfile = os.path.join(path, pat % lib)
+            if os.path.isfile(libfile):
+                found = True
+                break
+        if not found:
+            bad.append(libfile)
+    if bad:
+        libs = 'library' if len(bad) == 1 else 'libraries'
+        raise Exception('Missing %s: %s' % (libs, ', '.join(bad)))
diff --git a/src/beast/python/beast/util/Git.py b/src/beast/python/beast/util/Git.py
new file mode 100644
index 0000000000..31cecad47a
--- /dev/null
+++ b/src/beast/python/beast/util/Git.py
@@ -0,0 +1,9 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import os
+
+from beast.util import Execute
+from beast.util import String
+
+def describe(**kwds):
+    return String.single_line(Execute.execute('git describe --tags', **kwds))
diff --git a/src/beast/python/beast/util/Iter.py b/src/beast/python/beast/util/Iter.py
new file mode 100644
index 0000000000..976165cb53
--- /dev/null
+++ b/src/beast/python/beast/util/Iter.py
@@ -0,0 +1,7 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+def first(condition, sequence):
+    for i in sequence:
+        result = condition(i)
+        if result:
+            return result
diff --git a/src/beast/python/beast/util/String.py b/src/beast/python/beast/util/String.py
new file mode 100644
index 0000000000..63d89084fa
--- /dev/null
+++ b/src/beast/python/beast/util/String.py
@@ -0,0 +1,60 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import functools
+
+from beast.util import Iter
+from beast.util.Terminal import warn
+
+def is_string(s):
+    """Is s a string? - in either Python 2.x or 3.x."""
+    return isinstance(s, (str, unicode))
+
+def stringify(item, joiner=''):
+    """If item is not a string, stringify its members and join them."""
+    try:
+        len(item)
+    except:
+        return str(item)
+    if not item or is_string(item):
+        return item or ''
+    else:
+        return joiner.join(str(i) for i in item)
+
+def single_line(line, report_errors=True, joiner='+'):
+    """Force a string to be a single line with no carriage returns, and report
+    a warning if there was more than one line."""
+    lines = line.strip().splitlines()
+    if report_errors and len(lines) > 1:
+      print('multiline result:', lines)
+    return joiner.join(lines)
+
+# Copied from
+# https://github.com/lerugray/pickett/blob/master/pickett/ParseScript.py
+def remove_comment(line):
+    """Remove trailing comments from one line."""
+    start = 0
+    while True:
+        loc = line.find('#', start)
+        if loc == -1:
+            return line.replace('\\#', '#')
+        elif not (loc and line[loc - 1] == '\\'):
+            return line[:loc].replace('\\#', '#')
+        start = loc + 1
+
+def remove_quotes(line, quote='"', print=print):
+    if not line.startswith(quote):
+        return line
+    if line.endswith(quote):
+        return line[1:-1]
+
+    warn('line started with %s but didn\'t end with one:' % quote, print)
+    print(line)
+    return line[1:]
+
+def fields_after_prefix(prefix, line):
+    line = line.strip()
+    return line.startswith(prefix) and line[len(prefix):].split()
+
+def first_fields_after_prefix(prefix, sequence):
+    condition = functools.partial(fields_after_prefix, prefix)
+    return Iter.first(condition, sequence) or []
diff --git a/src/beast/python/beast/util/String_test.py b/src/beast/python/beast/util/String_test.py
new file mode 100644
index 0000000000..9e88b37be0
--- /dev/null
+++ b/src/beast/python/beast/util/String_test.py
@@ -0,0 +1,36 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from unittest import TestCase
+
+from beast.util import String
+from beast.util import Terminal
+
+Terminal.CAN_CHANGE_COLOR = False
+
+class String_test(TestCase):
+  def test_comments(self):
+    self.assertEqual(String.remove_comment(''), '')
+    self.assertEqual(String.remove_comment('#'), '')
+    self.assertEqual(String.remove_comment('# a comment'), '')
+    self.assertEqual(String.remove_comment('hello # a comment'), 'hello ')
+    self.assertEqual(String.remove_comment(
+      r'hello \# not a comment # a comment'),
+      'hello # not a comment ')
+
+  def test_remove_quotes(self):
+    errors = []
+    self.assertEqual(String.remove_quotes('hello', print=errors.append),
+                     'hello')
+    self.assertEqual(String.remove_quotes('"hello"', print=errors.append),
+                     'hello')
+    self.assertEqual(String.remove_quotes('hello"', print=errors.append),
+                     'hello"')
+    self.assertEqual(errors, [])
+
+  def test_remove_quotes_error(self):
+    errors = []
+    self.assertEqual(String.remove_quotes('"hello', print=errors.append),
+                     'hello')
+    self.assertEqual(errors,
+                     ['WARNING: line started with " but didn\'t end with one:',
+                      '"hello'])
diff --git a/src/beast/python/beast/util/Terminal.py b/src/beast/python/beast/util/Terminal.py
new file mode 100644
index 0000000000..d5b33c0894
--- /dev/null
+++ b/src/beast/python/beast/util/Terminal.py
@@ -0,0 +1,36 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import sys
+
+from beast.platform.Platform import PLATFORM
+
+# See https://stackoverflow.com/questions/7445658/how-to-detect-if-the-console-does-support-ansi-escape-codes-in-python
+CAN_CHANGE_COLOR = (
+    hasattr(sys.stderr, "isatty")
+    and sys.stderr.isatty()
+    and not PLATFORM.startswith('Windows'))
+
+
+# See https://en.wikipedia.org/wiki/ANSI_escape_code
+RED = 91
+GREEN = 92
+BLUE = 94
+
+def add_mode(text, *modes):
+    if CAN_CHANGE_COLOR:
+        modes = ';'.join(str(m) for m in modes)
+        return '\033[%sm%s\033[0m' % (modes, text)
+    else:
+        return text
+
+def blue(text):
+    return add_mode(text, BLUE)
+
+def green(text):
+    return add_mode(text, GREEN)
+
+def red(text):
+    return add_mode(text, RED)
+
+def warn(text, print=print):
+    print('%s %s' % (red('WARNING:'), text))
diff --git a/src/beast/python/beast/util/Tests.py b/src/beast/python/beast/util/Tests.py
new file mode 100644
index 0000000000..2ad1986ae9
--- /dev/null
+++ b/src/beast/python/beast/util/Tests.py
@@ -0,0 +1,31 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+import os
+
+from beast.util import File
+
+LIBS_PREFIX = '// LIBS:'
+MODS_PREFIX = '// MODULES:'
+
+def build_executable(env, path, main_program_file):
+    """Build a stand alone executable that runs
+       all the test suites in one source file."""
+    libs = File.first_fields_after_prefix(path, LIBS_PREFIX)
+    source_modules = File.first_fields_after_prefix(path, MODS_PREFIX)
+    source_modules = File.sibling_files(path, source_modules)
+
+    bin = os.path.basename(os.path.splitext(path)[0])
+    bin = os.path.join('bin', bin)
+
+    # All paths get normalized here, so we can use posix
+    # forward slashes for everything including on Windows
+    srcs = File.child_files('bin', [main_program_file, path] + source_modules)
+    objs = [File.replace_extension(f, '.o') for f in srcs]
+    if libs:
+        env.Append(LIBS=libs)  # DANGER: will append the file over and over.
+    env.Program(bin, srcs)
+
+def run_tests(env, main_program_file, root, suffix):
+    root = os.path.normpath(root)
+    for path in File.find_files_with_suffix(root, suffix):
+        build_executable(env, path, main_program_file)
diff --git a/src/beast/python/beast/util/__init__.py b/src/beast/python/beast/util/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/src/beast/python/clean-python.py b/src/beast/python/clean-python.py
new file mode 100755
index 0000000000..1a18804354
--- /dev/null
+++ b/src/beast/python/clean-python.py
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Remove all the compiled .pyc files at or below this directory.
+
+find . -name \*.pyc | xargs rm
diff --git a/src/beast/python/run-tests.sh b/src/beast/python/run-tests.sh
new file mode 100755
index 0000000000..0b181ca7ab
--- /dev/null
+++ b/src/beast/python/run-tests.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Run all the beast Python unit tests.
+
+python -m unittest discover -p \*_test.py