diff --git a/paramiko/py3compat.py b/paramiko/py3compat.py
new file mode 100644
index 0000000..c4a85ac
--- /dev/null
+++ b/paramiko/py3compat.py
@@ -0,0 +1,130 @@
+import sys
+
+__all__ = ['PY3', 'string_types', 'integer_types', 'text_type', 'bytes_type', 'long', 'input', 'bytestring', 'byte_ord', 'byte_chr', 'byte_mask', 'b', 'u', 'StringIO', 'BytesIO', 'is_callable', 'MAXSIZE', 'next']
+
+PY3 = sys.version_info[0] >= 3
+
+if PY3:
+    import collections
+    import struct
+    string_types = str
+    integer_types = int
+    text_type = str
+    bytes_type = bytes
+    long = int
+    input = input
+
+    def bytestring(s):
+        return s
+
+    def byte_ord(c):
+        assert isinstance(c, int)
+        return c
+
+    def byte_chr(c):
+        assert isinstance(c, int)
+        return struct.pack('B', c)
+
+    def byte_mask(c, mask):
+        assert isinstance(c, int)
+        return struct.pack('B', c & mask)
+
+    def b(s, encoding='utf8'):
+        """cast unicode or bytes to bytes"""
+        if isinstance(s, bytes):
+            return s
+        elif isinstance(s, str):
+            return s.encode(encoding)
+        else:
+            raise TypeError("Expected unicode or bytes, got %r" % s)
+
+    def u(s, encoding='utf8'):
+        """cast bytes or unicode to unicode"""
+        if isinstance(s, bytes):
+            return s.decode(encoding)
+        elif isinstance(s, str):
+            return s
+        else:
+            raise TypeError("Expected unicode or bytes, got %r" % s)
+
+    import io
+    StringIO = io.StringIO      # NOQA
+    BytesIO = io.BytesIO        # NOQA
+
+    def is_callable(c):
+        return isinstance(c, collections.Callable)
+
+    def get_next(c):
+        return c.__next__
+
+    next = next
+
+    MAXSIZE = sys.maxsize       # NOQA
+else:
+    string_types = basestring
+    integer_types = (int, long)
+    text_type = unicode
+    bytes_type = str
+    long = long
+    input = raw_input
+
+    def bytestring(s):  # NOQA
+        if isinstance(s, unicode):
+            return s.encode('utf-8')
+        return s
+
+    byte_ord = ord  # NOQA
+    byte_chr = chr  # NOQA
+
+    def byte_mask(c, mask):
+        return chr(ord(c) & mask)
+
+    def b(s, encoding='utf8'):  # NOQA
+        """cast unicode or bytes to bytes"""
+        if isinstance(s, str):
+            return s
+        elif isinstance(s, unicode):
+            return s.encode(encoding)
+        else:
+            raise TypeError("Expected unicode or bytes, got %r" % s)
+
+    def u(s, encoding='utf8'):  # NOQA
+        """cast bytes or unicode to unicode"""
+        if isinstance(s, str):
+            return s.decode(encoding)
+        elif isinstance(s, unicode):
+            return s
+        else:
+            raise TypeError("Expected unicode or bytes, got %r" % s)
+
+    try:
+        import cStringIO
+        StringIO = cStringIO.StringIO   # NOQA
+    except ImportError:
+        import StringIO
+        StringIO = StringIO.StringIO    # NOQA
+
+    BytesIO = StringIO
+
+    def is_callable(c):  # NOQA
+        return callable(c)
+
+    def get_next(c):  # NOQA
+        return c.next
+
+    def next(c):
+        return c.next()
+
+    # It's possible to have sizeof(long) != sizeof(Py_ssize_t).
+    class X(object):
+        def __len__(self):
+            return 1 << 31
+    try:
+        len(X())
+    except OverflowError:
+        # 32-bit
+        MAXSIZE = int((1 << 31) - 1)        # NOQA
+    else:
+        # 64-bit
+        MAXSIZE = int((1 << 63) - 1)        # NOQA
+    del X