diff --git a/Docs/src/SConscript b/Docs/src/SConscript
index e0241c96..6cbf996a 100644
--- a/Docs/src/SConscript
+++ b/Docs/src/SConscript
@@ -50,8 +50,8 @@ chapters = 5
 appendices = 9
 
 htmls = Split('IndexPage.html Contents.html') \
-	+ map(lambda ch: 'Chapter' + str(ch + 1) + '.html', range(chapters)) \
-	+ map(lambda ap: 'Appendix' + chr(ord('A') + ap) + '.html', range(appendices))
+	+ list(map(lambda ch: 'Chapter' + str(ch + 1) + '.html', range(chapters))) \
+	+ list(map(lambda ap: 'Appendix' + chr(ord('A') + ap) + '.html', range(appendices)))
 
 docsdefault_install_basepath = 'Docs'
 
@@ -137,7 +137,7 @@ def docs_fixer(target, source, env):
 		data = open(html.path,'rb').read()
 
 		for pat, repl in fixes.items():
-			data = re.sub(env.subst(pat), env.subst(repl), data)
+			data = re.sub(env.subst(pat).encode(), env.subst(repl).encode(), data)
 
 		open(html.path, 'wb').write(data)
 
diff --git a/SCons/Tools/crossmingw.py b/SCons/Tools/crossmingw.py
index b628d8d6..522eaf29 100644
--- a/SCons/Tools/crossmingw.py
+++ b/SCons/Tools/crossmingw.py
@@ -106,7 +106,7 @@ def shlib_emitter(target, source, env):
     no_import_lib = env.get('no_import_lib', 0)
 
     if not dll:
-        raise SCons.Errors.UserError, "A shared library should have exactly one target with the suffix: %s" % env.subst("$SHLIBSUFFIX")
+        raise SCons.Errors.UserError("A shared library should have exactly one target with the suffix: %s" % env.subst("$SHLIBSUFFIX"))
     
     if not no_import_lib and \
        not env.FindIxes(target, 'LIBPREFIX', 'LIBSUFFIX'):
@@ -149,9 +149,9 @@ def generate(env):
         if not path: 
             path = []
         if SCons.Util.is_String(path):
-            path = string.split(path, os.pathsep)
+            path = str.split(path, os.pathsep)
 
-        env['ENV']['PATH'] = string.join([dir] + path, os.pathsep)
+        env['ENV']['PATH'] = str.join(os.pathsep, [dir] + path)
 
     # Most of mingw is the same as gcc and friends...
     gnu_tools = ['gcc', 'g++', 'gnulink', 'ar', 'gas']
diff --git a/SCons/utils.py b/SCons/utils.py
index 372f8ae5..0b5315e9 100644
--- a/SCons/utils.py
+++ b/SCons/utils.py
@@ -123,11 +123,11 @@ def GetOptionOrEnv(name, defval = None):
 	Get option set on scons command line or in os.environ
 	"""
 	import os
-	#if optenv and optenv.has_key(name):
+	#if optenv and name in optenv:
 	#	return optenv[name]
-	if ARGUMENTS.has_key(name):
+	if name in ARGUMENTS:
 		return ARGUMENTS[name]
-	if os.environ.has_key(name):
+	if name in os.environ:
 		return os.environ[name]
 	return defval
 
diff --git a/SConstruct b/SConstruct
index a0b417c0..e8252c97 100644
--- a/SConstruct
+++ b/SConstruct
@@ -1,4 +1,5 @@
 EnsureSConsVersion(1,2)
+EnsurePythonVersion(2,7)
 
 stubs = [
 	'bzip2',
@@ -253,14 +254,14 @@ f = open(defenv.File('#$BUILD_CONFIG/nsis-version.h').abspath, 'w')
 f.write('// This file is automatically generated by SCons\n// DO NOT EDIT THIS FILE\n')
 f.write('#include "%s"\n' % File('#/Source/tchar.h').abspath)
 
-if (not defenv.has_key('VER_PACKED')) and defenv.has_key('VER_MAJOR') and defenv.has_key('VER_MINOR'):
+if (not 'VER_PACKED' in defenv) and 'VER_MAJOR' in defenv and 'VER_MINOR' in defenv:
 	packed_r = int(defenv.get('VER_REVISION','0'))
 	packed_b = int(defenv.get('VER_BUILD','0'))
 	defenv['VER_PACKED'] = '0x%0.2i%0.3i%0.2i%0.1i' % (int(defenv['VER_MAJOR']), int(defenv['VER_MINOR']), packed_r, packed_b)
-if not defenv.has_key('VER_PACKED'):
+if not 'VER_PACKED' in defenv:
 	import re
 	found = None
-	for v in re.compile(r'^\\H\{[v]?(\S+)\}', re.M).finditer(File('#/Docs/src/history.but').get_contents()): # Try to parse the Halibut history file
+	for v in re.compile(r'^\\H\{[v]?(\S+)\}', re.M).finditer(File('#/Docs/src/history.but').get_contents().decode()): # Try to parse the Halibut history file
 		if v and not found:
 			v = v.group(1).split('.')
 			if len(v) >= 2:
@@ -277,11 +278,11 @@ if int(defenv['VER_PACKED'], 0) < int('0x03000000', 0) or int(defenv['VER_PACKED
 	Exit(1)
 f.write('#define NSIS_PACKEDVERSION _T("%s")\n' % defenv['VER_PACKED'])
 
-if defenv.has_key('VER_MAJOR') and defenv.get('VERSION','') == '':
+if 'VER_MAJOR' in defenv and defenv.get('VERSION','') == '':
 	defenv['VERSION'] = defenv['VER_MAJOR']
-	if defenv.has_key('VER_MINOR'):
+	if 'VER_MINOR' in defenv:
 		defenv['VERSION'] += '.' + defenv['VER_MINOR']
-	if defenv.has_key('VER_REVISION'):
+	if 'VER_REVISION' in defenv:
 		defenv['VERSION'] += '.' + defenv['VER_REVISION']
 f.write('#define NSIS_VERSION _T("v%s")\n' % defenv['VERSION'])
 
@@ -292,7 +293,7 @@ f.close()
 ######################################################################
 
 def GetArcCPU(env):
-	if (not env.has_key('TARGET_ARCH')) or env['TARGET_ARCH'] == 'x86':
+	if (not 'TARGET_ARCH' in env) or env['TARGET_ARCH'] == 'x86':
 		return 'x86'
 	return env['TARGET_ARCH']
 
@@ -355,7 +356,7 @@ defenv['DISTSUFFIX'] = ''
 
 if GetArcCPU(defenv) != 'x86':
 	defenv['DISTSUFFIX'] += GetArcCPU(defenv)
-if defenv.has_key('CODESIGNER'):
+if 'CODESIGNER' in defenv:
 	defenv['DISTSUFFIX'] += '-signed'
 
 defenv.Execute(Delete('$ZIPDISTDIR'))
@@ -363,21 +364,19 @@ defenv.Execute(Delete('$INSTDISTDIR'))
 defenv.Execute(Delete('$TESTDISTDIR'))
 
 def Distribute(files, names, component, path, subpath, alias, install_alias=None):
-	from types import StringType
-
 	files = MakeFileList(files)
 
 	names = names or map(lambda x: x.name, files)
-	if isinstance(names, StringType):
+	if isinstance(names, str):
 		names = [names]
 
 	for d in ('$ZIPDISTDIR', '$INSTDISTDIR', '$TESTDISTDIR'):
-		paths = map(lambda file: os.path.join(d, path, subpath, file), names)
+		paths = list(map(lambda file: os.path.join(d, path, subpath, file), names))
 		defenv.InstallAs(paths, files)
 
-	if (defenv.has_key('PREFIX') and defenv['PREFIX']) or (defenv.has_key('PREFIX_DEST') and defenv['PREFIX_DEST']) :
+	if ('PREFIX' in defenv and defenv['PREFIX']) or ('PREFIX_DEST' in defenv and defenv['PREFIX_DEST']) :
 		prefix = '${PREFIX_DEST}${PREFIX_%s}' % component.upper()
-		paths = map(lambda file: os.path.join(prefix, path, subpath, file), names)
+		paths = list(map(lambda file: os.path.join(prefix, path, subpath, file), names))
 		ins = defenv.InstallAs(paths, files)
 	else:
 		ins = []
@@ -434,7 +433,7 @@ def FindMakeNSIS(env, path):
 	return exename
 
 def Sign(targets):
-	if defenv.has_key('CODESIGNER'):
+	if 'CODESIGNER' in defenv:
 		for t in targets:
 			a = defenv.Action('$CODESIGNER "%s"' % t.path)
 			defenv.AddPostAction(t, a)
@@ -571,8 +570,8 @@ else:
 	optchar = '-'
 
 defenv['INSTVER'] = '%sDVERSION=$VERSION' % optchar
-if defenv.has_key('VER_MAJOR') and defenv.has_key('VER_MINOR') \
-    and defenv.has_key('VER_REVISION') and defenv.has_key('VER_BUILD'):
+if 'VER_MAJOR' in defenv and 'VER_MINOR' in defenv \
+    and 'VER_REVISION' in defenv and 'VER_BUILD' in defenv:
 	defenv['INSTVER'] += ' %sDVER_MAJOR=$VER_MAJOR' % optchar
 	defenv['INSTVER'] += ' %sDVER_MINOR=$VER_MINOR' % optchar
 	defenv['INSTVER'] += ' %sDVER_REVISION=$VER_REVISION' % optchar