Use absolute import everywhere
This prevents Python 2.7 from attempting to import system modules
like sys and ctypes from the 'serial' directory.
diff --git a/serial/__init__.py b/serial/__init__.py
index c24ced8..dcd7c12 100644
--- a/serial/__init__.py
+++ b/serial/__init__.py
@@ -7,6 +7,8 @@
#
# SPDX-License-Identifier: BSD-3-Clause
+from __future__ import absolute_import
+
import sys
import importlib
diff --git a/serial/rfc2217.py b/serial/rfc2217.py
index e8ddb7f..c35aa9b 100644
--- a/serial/rfc2217.py
+++ b/serial/rfc2217.py
@@ -58,6 +58,8 @@
# RFC).
# the order of the options is not relevant
+from __future__ import absolute_import
+
import logging
import socket
import struct
diff --git a/serial/rs485.py b/serial/rs485.py
index 2939350..d7aff6f 100644
--- a/serial/rs485.py
+++ b/serial/rs485.py
@@ -13,6 +13,8 @@
NOTE: Some implementations may only support a subset of the settings.
"""
+from __future__ import absolute_import
+
import time
import serial
diff --git a/serial/serialcli.py b/serial/serialcli.py
index 0727a52..ddd0cdf 100644
--- a/serial/serialcli.py
+++ b/serial/serialcli.py
@@ -7,6 +7,8 @@
#
# SPDX-License-Identifier: BSD-3-Clause
+from __future__ import absolute_import
+
import System
import System.IO.Ports
from serial.serialutil import *
diff --git a/serial/serialjava.py b/serial/serialjava.py
index 7bd5b3e..9c920c5 100644
--- a/serial/serialjava.py
+++ b/serial/serialjava.py
@@ -7,6 +7,8 @@
#
# SPDX-License-Identifier: BSD-3-Clause
+from __future__ import absolute_import
+
from serial.serialutil import *
diff --git a/serial/serialposix.py b/serial/serialposix.py
index 3ac6283..82fe59a 100644
--- a/serial/serialposix.py
+++ b/serial/serialposix.py
@@ -26,6 +26,8 @@
# - aix (AIX) /dev/tty%d
+from __future__ import absolute_import
+
# pylint: disable=abstract-method
import errno
import fcntl
diff --git a/serial/serialutil.py b/serial/serialutil.py
index 7d51752..e847a6a 100644
--- a/serial/serialutil.py
+++ b/serial/serialutil.py
@@ -7,6 +7,8 @@
#
# SPDX-License-Identifier: BSD-3-Clause
+from __future__ import absolute_import
+
import io
import time
diff --git a/serial/serialwin32.py b/serial/serialwin32.py
index 7b88999..74bfd05 100644
--- a/serial/serialwin32.py
+++ b/serial/serialwin32.py
@@ -9,6 +9,8 @@
#
# Initial patch to use ctypes by Giovanni Bajo <rasky@develer.com>
+from __future__ import absolute_import
+
# pylint: disable=invalid-name,too-few-public-methods
import ctypes
import time
diff --git a/serial/threaded/__init__.py b/serial/threaded/__init__.py
index 74b6924..9b8fa01 100644
--- a/serial/threaded/__init__.py
+++ b/serial/threaded/__init__.py
@@ -9,6 +9,8 @@
"""\
Support threading with serial ports.
"""
+from __future__ import absolute_import
+
import serial
import threading
diff --git a/serial/tools/hexlify_codec.py b/serial/tools/hexlify_codec.py
index 1371da2..bd8f6b0 100644
--- a/serial/tools/hexlify_codec.py
+++ b/serial/tools/hexlify_codec.py
@@ -18,6 +18,8 @@
"""
+from __future__ import absolute_import
+
import codecs
import serial
diff --git a/serial/tools/list_ports.py b/serial/tools/list_ports.py
index 827e81f..0d7e3d4 100644
--- a/serial/tools/list_ports.py
+++ b/serial/tools/list_ports.py
@@ -16,6 +16,8 @@
based on their descriptions or hardware ID.
"""
+from __future__ import absolute_import
+
import sys
import os
import re
diff --git a/serial/tools/list_ports_common.py b/serial/tools/list_ports_common.py
index aa91e5e..1781929 100644
--- a/serial/tools/list_ports_common.py
+++ b/serial/tools/list_ports_common.py
@@ -7,6 +7,9 @@
# (C) 2015 Chris Liechti <cliechti@gmx.net>
#
# SPDX-License-Identifier: BSD-3-Clause
+
+from __future__ import absolute_import
+
import re
import glob
import os
diff --git a/serial/tools/list_ports_linux.py b/serial/tools/list_ports_linux.py
index 4ee7877..3f7eadb 100644
--- a/serial/tools/list_ports_linux.py
+++ b/serial/tools/list_ports_linux.py
@@ -8,6 +8,8 @@
#
# SPDX-License-Identifier: BSD-3-Clause
+from __future__ import absolute_import
+
import glob
import os
from serial.tools import list_ports_common
diff --git a/serial/tools/list_ports_osx.py b/serial/tools/list_ports_osx.py
index 79ce4f1..f46a820 100644
--- a/serial/tools/list_ports_osx.py
+++ b/serial/tools/list_ports_osx.py
@@ -21,6 +21,8 @@
# Also see the 'IORegistryExplorer' for an idea of what we are actually searching
+from __future__ import absolute_import
+
import ctypes
import ctypes.util
diff --git a/serial/tools/list_ports_posix.py b/serial/tools/list_ports_posix.py
index 0d580b0..79bc8ed 100644
--- a/serial/tools/list_ports_posix.py
+++ b/serial/tools/list_ports_posix.py
@@ -16,6 +16,8 @@
currently just identical to the port name.
"""
+from __future__ import absolute_import
+
import glob
import sys
import os
diff --git a/serial/tools/list_ports_windows.py b/serial/tools/list_ports_windows.py
index f28047b..9159f5d 100644
--- a/serial/tools/list_ports_windows.py
+++ b/serial/tools/list_ports_windows.py
@@ -8,6 +8,8 @@
#
# SPDX-License-Identifier: BSD-3-Clause
+from __future__ import absolute_import
+
# pylint: disable=invalid-name,too-few-public-methods
import re
import ctypes
diff --git a/serial/tools/miniterm.py b/serial/tools/miniterm.py
index 812f146..b0804ba 100644
--- a/serial/tools/miniterm.py
+++ b/serial/tools/miniterm.py
@@ -7,6 +7,8 @@
#
# SPDX-License-Identifier: BSD-3-Clause
+from __future__ import absolute_import
+
import codecs
import os
import sys
diff --git a/serial/urlhandler/protocol_alt.py b/serial/urlhandler/protocol_alt.py
index c14a87e..2e666ca 100644
--- a/serial/urlhandler/protocol_alt.py
+++ b/serial/urlhandler/protocol_alt.py
@@ -16,6 +16,8 @@
# use poll based implementation on Posix (Linux):
# python -m serial.tools.miniterm alt:///dev/ttyUSB0?class=PosixPollSerial
+from __future__ import absolute_import
+
try:
import urlparse
except ImportError:
diff --git a/serial/urlhandler/protocol_hwgrep.py b/serial/urlhandler/protocol_hwgrep.py
index 49bbebe..1a288c9 100644
--- a/serial/urlhandler/protocol_hwgrep.py
+++ b/serial/urlhandler/protocol_hwgrep.py
@@ -20,6 +20,8 @@
# n=<N> pick the N'th entry instead of the first one (numbering starts at 1)
# skip_busy tries to open port to check if it is busy, fails on posix as ports are not locked!
+from __future__ import absolute_import
+
import serial
import serial.tools.list_ports
diff --git a/serial/urlhandler/protocol_loop.py b/serial/urlhandler/protocol_loop.py
index 7bf6cf9..985e7a7 100644
--- a/serial/urlhandler/protocol_loop.py
+++ b/serial/urlhandler/protocol_loop.py
@@ -13,6 +13,8 @@
# URL format: loop://[option[/option...]]
# options:
# - "debug" print diagnostic messages
+from __future__ import absolute_import
+
import logging
import numbers
import time
diff --git a/serial/urlhandler/protocol_rfc2217.py b/serial/urlhandler/protocol_rfc2217.py
index 1898803..8be310f 100644
--- a/serial/urlhandler/protocol_rfc2217.py
+++ b/serial/urlhandler/protocol_rfc2217.py
@@ -7,4 +7,6 @@
#
# SPDX-License-Identifier: BSD-3-Clause
+from __future__ import absolute_import
+
from serial.rfc2217 import Serial # noqa
diff --git a/serial/urlhandler/protocol_socket.py b/serial/urlhandler/protocol_socket.py
index 5c77415..36cdf1f 100644
--- a/serial/urlhandler/protocol_socket.py
+++ b/serial/urlhandler/protocol_socket.py
@@ -16,6 +16,8 @@
# options:
# - "debug" print diagnostic messages
+from __future__ import absolute_import
+
import errno
import logging
import select
diff --git a/serial/urlhandler/protocol_spy.py b/serial/urlhandler/protocol_spy.py
index 3479010..92aaa2e 100644
--- a/serial/urlhandler/protocol_spy.py
+++ b/serial/urlhandler/protocol_spy.py
@@ -20,6 +20,8 @@
# redirect output to an other terminal window on Posix (Linux):
# python -m serial.tools.miniterm spy:///dev/ttyUSB0?dev=/dev/pts/14\&color
+from __future__ import absolute_import
+
import sys
import time
diff --git a/serial/win32.py b/serial/win32.py
index 905ce0f..08b6e67 100644
--- a/serial/win32.py
+++ b/serial/win32.py
@@ -9,6 +9,8 @@
# pylint: disable=invalid-name,too-few-public-methods,protected-access,too-many-instance-attributes
+from __future__ import absolute_import
+
from ctypes import c_ulong, c_void_p, c_int64, c_char, \
WinDLL, sizeof, Structure, Union, POINTER
from ctypes.wintypes import HANDLE