diff --git a/Makefile b/Makefile
index 702bda9..e9abc76 100644
--- a/Makefile
+++ b/Makefile
@@ -28,7 +28,7 @@ tests:
 
 	flake8 --exclude=__init__.py,memory_profiler.py pycallgraph
 	flake8 --ignore=F403 test
-	flake8 examples
+	flake8 examples --exclude=all.py
 
 doc:
 	cd docs/examples && ./generate.py
diff --git a/examples/gephi/basic.py b/examples/gephi/basic.py
index 1f15fcc..14b15f2 100755
--- a/examples/gephi/basic.py
+++ b/examples/gephi/basic.py
@@ -34,7 +34,7 @@ def main():
 
     with PyCallGraph(output=gephi):
         person = Person()
-        for a in xrange(10):
+        for a in range(10):
             person.add_banana(Banana())
         person.eat_bananas()
 
diff --git a/examples/graphviz/basic.py b/examples/graphviz/basic.py
index 6404af5..63b476a 100755
--- a/examples/graphviz/basic.py
+++ b/examples/graphviz/basic.py
@@ -34,7 +34,7 @@ def main():
 
     with PyCallGraph(output=graphviz):
         person = Person()
-        for a in xrange(10):
+        for a in range(10):
             person.add_banana(Banana())
         person.eat_bananas()
 
diff --git a/examples/graphviz/example_with_submodules/example_with_submodules.py b/examples/graphviz/example_with_submodules/example_with_submodules.py
index 2fb6d04..0324c4b 100644
--- a/examples/graphviz/example_with_submodules/example_with_submodules.py
+++ b/examples/graphviz/example_with_submodules/example_with_submodules.py
@@ -9,5 +9,6 @@ def main():
     s2 = SubmoduleTwo()
     s2.report()
 
+
 if __name__ == "__main__":
     main()
diff --git a/examples/graphviz/recursive.py b/examples/graphviz/recursive.py
index d61a1b1..749a737 100755
--- a/examples/graphviz/recursive.py
+++ b/examples/graphviz/recursive.py
@@ -17,8 +17,9 @@ def main():
     graphviz.output_file = 'recursive.png'
 
     with PyCallGraph(output=graphviz):
-        for a in xrange(1, 10):
+        for a in range(1, 10):
             factorial(a)
 
+
 if __name__ == '__main__':
     main()
diff --git a/examples/graphviz/regexp.py b/examples/graphviz/regexp.py
old mode 100755
new mode 100644
index 63bb2c2..4054668
--- a/examples/graphviz/regexp.py
+++ b/examples/graphviz/regexp.py
@@ -15,11 +15,11 @@ def main():
     config = Config(include_stdlib=True)
 
     with PyCallGraph(output=graphviz, config=config):
-        reo = compile()
+        reo = compile_regex()
         match(reo)
 
 
-def compile():
+def compile_regex():
     return re.compile('^[abetors]*$')
 
 
@@ -41,5 +41,6 @@ def words():
         'abrasives',
     ]
 
+
 if __name__ == '__main__':
     main()
diff --git a/pycallgraph/config.py b/pycallgraph/config.py
index 2bce930..54d717c 100755
--- a/pycallgraph/config.py
+++ b/pycallgraph/config.py
@@ -1,4 +1,5 @@
 import argparse
+import operator
 import sys
 
 from .output import outputters
@@ -6,6 +7,11 @@
 from .grouper import Grouper
 
 
+iteritems = operator.methodcaller('iteritems'
+                                  if sys.version_info < (3, ) else
+                                  'items')
+
+
 class Config(object):
     '''Handles configuration settings for pycallgraph, tracer, and each output
     module.  It also handles command line arguments.
@@ -38,7 +44,7 @@ def __init__(self, **kwargs):
         self.did_init = True
 
         # Update the defaults with anything from kwargs
-        [setattr(self, k, v) for k, v in kwargs.iteritems()]
+        [setattr(self, k, v) for k, v in iteritems(kwargs)]
 
         self.create_parser()
 
diff --git a/pycallgraph/output/graphviz.py b/pycallgraph/output/graphviz.py
index e875e39..e04c2a3 100644
--- a/pycallgraph/output/graphviz.py
+++ b/pycallgraph/output/graphviz.py
@@ -1,7 +1,9 @@
 from __future__ import division
 
 import tempfile
+import operator
 import os
+import sys
 import textwrap
 import subprocess as sub
 
@@ -11,6 +13,11 @@
 from .output import Output
 
 
+iteritems = operator.methodcaller('iteritems'
+                                  if sys.version_info < (3, ) else
+                                  'items')
+
+
 class GraphvizOutput(Output):
 
     def __init__(self, **kwargs):
@@ -151,7 +158,7 @@ def generate(self):
 
     def attrs_from_dict(self, d):
         output = []
-        for attr, val in d.iteritems():
+        for attr, val in iteritems(d):
             output.append('%s = "%s"' % (attr, val))
         return ', '.join(output)
 
@@ -167,7 +174,7 @@ def edge(self, edge, attr):
 
     def generate_attributes(self):
         output = []
-        for section, attrs in self.graph_attributes.iteritems():
+        for section, attrs in iteritems(self.graph_attributes):
             output.append('{0} [ {1} ];'.format(
                 section, self.attrs_from_dict(attrs),
             ))
diff --git a/pycallgraph/output/output.py b/pycallgraph/output/output.py
index 662d563..c88768f 100644
--- a/pycallgraph/output/output.py
+++ b/pycallgraph/output/output.py
@@ -1,10 +1,16 @@
-import re
+import operator
 import os
+import re
+import sys
 from distutils.spawn import find_executable
 
 from ..exceptions import PyCallGraphException
 from ..color import Color
 
+iteritems = operator.methodcaller('iteritems'
+                                  if sys.version_info < (3, ) else
+                                  'items')
+
 
 class Output(object):
     '''Base class for all outputters.'''
@@ -16,14 +22,14 @@ def __init__(self, **kwargs):
         self.edge_label_func = self.edge_label
 
         # Update the defaults with anything from kwargs
-        [setattr(self, k, v) for k, v in kwargs.iteritems()]
+        [setattr(self, k, v) for k, v in iteritems(kwargs)]
 
     def set_config(self, config):
         '''
         This is a quick hack to move the config variables set in Config into
         the output module config variables.
         '''
-        for k, v in config.__dict__.iteritems():
+        for k, v in iteritems(config.__dict__):
             if hasattr(self, k) and \
                     callable(getattr(self, k)):
                 continue
@@ -116,7 +122,7 @@ def debug(self, text):
         self.processor.config.log_debug(text)
 
     @classmethod
-    def add_output_file(cls, subparser, defaults, help):
+    def add_output_file(cls, subparser, defaults, help):  # noqa: A002
         subparser.add_argument(
             '-o', '--output-file', type=str, default=defaults.output_file,
             help=help,
diff --git a/pycallgraph/pycallgraph.py b/pycallgraph/pycallgraph.py
index 6af5428..73e018b 100644
--- a/pycallgraph/pycallgraph.py
+++ b/pycallgraph/pycallgraph.py
@@ -33,7 +33,7 @@ def __init__(self, output=None, config=None):
     def __enter__(self):
         self.start()
 
-    def __exit__(self, type, value, traceback):
+    def __exit__(self, type, value, traceback):  # noqa: A002
         self.done()
 
     def get_tracer_class(self):
diff --git a/pycallgraph/tracer.py b/pycallgraph/tracer.py
index ffcab15..42319a8 100644
--- a/pycallgraph/tracer.py
+++ b/pycallgraph/tracer.py
@@ -1,8 +1,9 @@
 from __future__ import division
 
 import inspect
-import sys
+import operator
 import os
+import sys
 import time
 from distutils import sysconfig
 from collections import defaultdict
@@ -15,6 +16,11 @@
 from .util import Util
 
 
+iteritems = operator.methodcaller('iteritems'
+                                  if sys.version_info < (3, ) else
+                                  'items')
+
+
 class SyncronousTracer(object):
 
     def __init__(self, outputs, config):
@@ -294,7 +300,7 @@ def groups(self):
         grp = defaultdict(list)
         for node in self.nodes():
             grp[node.group].append(node)
-        for g in grp.iteritems():
+        for g in iteritems(grp):
             yield g
 
     def stat_group_from_func(self, func, calls):
@@ -312,14 +318,14 @@ def stat_group_from_func(self, func, calls):
         return stat_group
 
     def nodes(self):
-        for func, calls in self.func_count.iteritems():
+        for func, calls in iteritems(self.func_count):
             yield self.stat_group_from_func(func, calls)
 
     def edges(self):
-        for src_func, dests in self.call_dict.iteritems():
+        for src_func, dests in iteritems(self.call_dict):
             if not src_func:
                 continue
-            for dst_func, calls in dests.iteritems():
+            for dst_func, calls in iteritems(dests):
                 edge = self.stat_group_from_func(dst_func, calls)
                 edge.src_func = src_func
                 edge.dst_func = dst_func
@@ -372,4 +378,5 @@ def wrapper(*rest):
 
     return wrapper
 
+
 inspect.getmodule = simple_memoize(inspect.getmodule)
diff --git a/setup.py b/setup.py
index a2a2380..4641eb3 100755
--- a/setup.py
+++ b/setup.py
@@ -1,13 +1,13 @@
 #!/usr/bin/env python
 
-from os import path
-from setuptools import setup
 import sys
 
+from setuptools import setup
 from setuptools.command.test import test as TestCommand
 
 import pycallgraph
 
+
 # Only install the man page if the correct directory exists
 # XXX: Commented because easy_install doesn't like it
 #man_path = '/usr/share/man/man1/'
@@ -15,8 +15,8 @@
 #    data_files=[['/usr/share/man/man1/', ['man/pycallgraph.1']]]
 #else:
 #    data_files=None
+data_files = None
 
-data_files=None
 
 class PyTest(TestCommand):
 
@@ -30,6 +30,7 @@ def run_tests(self):
         errno = pytest.main(self.test_args)
         sys.exit(errno)
 
+
 setup(
     name='pycallgraph',
     version=pycallgraph.__version__,
@@ -45,15 +46,15 @@ def run_tests(self):
     use_2to3=True,
 
     # TODO: Update download_url
-    download_url =
-    'http://pycallgraph.slowchop.com/files/download/pycallgraph-%s.tar.gz' % \
-        pycallgraph.__version__,
+    download_url=
+    'http://pycallgraph.slowchop.com/files/download/pycallgraph-%s.tar.gz' %
+    pycallgraph.__version__,
 
     # Testing
     tests_require=['pytest'],
-    cmdclass = {'test': PyTest},
+    cmdclass={'test': PyTest},
 
-    classifiers = [
+    classifiers=[
         'Development Status :: 4 - Beta',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: GNU General Public License (GPL)',
@@ -68,4 +69,3 @@ def run_tests(self):
         'Topic :: Software Development :: Debuggers',
     ],
 )
-
diff --git a/test/conftest.py b/test/conftest.py
index b54e253..b8b7a0f 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -1,6 +1,7 @@
+from pycallgraph import PyCallGraph, Config
 import tempfile
 
-from helpers import *
+import pytest
 
 
 @pytest.fixture(scope='module')
diff --git a/test/helpers.py b/test/helpers.py
index 4ea4abb..0bbee37 100644
--- a/test/helpers.py
+++ b/test/helpers.py
@@ -1,13 +1,6 @@
 # flake8: noqa
 import time
 
-import pytest
-
-import fix_path
-from pycallgraph import *
-from pycallgraph.tracer import *
-from pycallgraph.output import *
-
 
 def wait_100ms():
     time.sleep(0.1)
diff --git a/test/test_color.py b/test/test_color.py
index 0d33fc5..535a577 100644
--- a/test/test_color.py
+++ b/test/test_color.py
@@ -1,4 +1,6 @@
-from helpers import *
+from pycallgraph import ColorException, Color
+
+import pytest
 
 
 def test_bad_range():
diff --git a/test/test_config.py b/test/test_config.py
index 5d5335f..ce0cbc2 100644
--- a/test/test_config.py
+++ b/test/test_config.py
@@ -1,4 +1,4 @@
-from helpers import *
+from pycallgraph.config import Config
 
 
 def test_init():
diff --git a/test/test_gephi.py b/test/test_gephi.py
index 15dd708..f3f2dfa 100644
--- a/test/test_gephi.py
+++ b/test/test_gephi.py
@@ -1,5 +1,10 @@
-from helpers import *
-from calls import *
+from pycallgraph import PyCallGraph
+from pycallgraph.output.gephi import GephiOutput
+import os
+
+import pytest
+
+from calls import one_nop
 
 
 @pytest.fixture
diff --git a/test/test_graphviz.py b/test/test_graphviz.py
index 35d8d8e..2669aed 100644
--- a/test/test_graphviz.py
+++ b/test/test_graphviz.py
@@ -1,5 +1,10 @@
-from helpers import *
-from calls import *
+from pycallgraph.output.graphviz import GraphvizOutput
+from pycallgraph.pycallgraph import PyCallGraph
+import os
+
+import pytest
+
+from calls import one_nop
 
 
 @pytest.fixture
diff --git a/test/test_output.py b/test/test_output.py
index 9149e5c..6b17775 100644
--- a/test/test_output.py
+++ b/test/test_output.py
@@ -1,4 +1,5 @@
-from helpers import *
+from pycallgraph import Config
+from pycallgraph.output import Output
 
 
 def test_set_config():
diff --git a/test/test_pycallgraph.py b/test/test_pycallgraph.py
index bdc7dc4..76a2fba 100644
--- a/test/test_pycallgraph.py
+++ b/test/test_pycallgraph.py
@@ -1,4 +1,7 @@
-from helpers import *
+from pycallgraph.exceptions import PyCallGraphException
+from pycallgraph.tracer import AsyncronousTracer, SyncronousTracer
+
+import pytest
 
 
 def test_start_no_outputs(pycg):
diff --git a/test/test_script.py b/test/test_script.py
index 0aa9016..fad47e1 100644
--- a/test/test_script.py
+++ b/test/test_script.py
@@ -1,7 +1,5 @@
 import subprocess
 
-from helpers import *
-
 
 def execute(arguments):
     command = 'PYTHONPATH=. scripts/pycallgraph ' + arguments
diff --git a/test/test_trace_processor.py b/test/test_trace_processor.py
index bdf16cc..7b8a0cf 100644
--- a/test/test_trace_processor.py
+++ b/test/test_trace_processor.py
@@ -1,9 +1,11 @@
+from pycallgraph.tracer import TraceProcessor
 import re
 import sys
 
-from helpers import *
-import calls
-from pycallgraph.tracer import TraceProcessor
+import pytest
+
+from pycallgraph import Config
+from calls import one_nop, nop
 
 
 @pytest.fixture
@@ -20,7 +22,7 @@ def test_empty(trace_processor):
 
 def test_nop(trace_processor):
     sys.settrace(trace_processor.process)
-    calls.nop()
+    nop()
     sys.settrace(None)
 
     assert trace_processor.call_dict == {
@@ -32,7 +34,7 @@ def test_nop(trace_processor):
 
 def test_one_nop(trace_processor):
     sys.settrace(trace_processor.process)
-    calls.one_nop()
+    one_nop()
     sys.settrace(None)
 
     assert trace_processor.call_dict == {
@@ -45,7 +47,7 @@ def stdlib_trace(trace_processor, include_stdlib):
     trace_processor.config = Config(include_stdlib=include_stdlib)
     sys.settrace(trace_processor.process)
     re.match("asdf", "asdf")
-    calls.one_nop()
+    one_nop()
     sys.settrace(None)
     return trace_processor.call_dict
 
diff --git a/test/test_util.py b/test/test_util.py
index 084c6f3..bf8cf09 100644
--- a/test/test_util.py
+++ b/test/test_util.py
@@ -1,4 +1,4 @@
-from helpers import *
+from pycallgraph.util import Util
 
 
 def test_human_readable_biyte():