Python 2 cleanup (#17583)

* Drop _cy2

* Drop Python 2 specific code in mxnet and tests

* Replace io.open with open

* Drop from __future__ imports

* Fix lint

CMakeLists.txt

@@ -897,7 +897,7 @@ add_custom_target(mxnet_lint COMMAND ${CMAKE_COMMAND} -DMSVC=${MSVC} -DPYTHON_EX
 if(BUILD_CYTHON_MODULES)
   include(cmake/BuildCythonModules.cmake)
   add_cython_modules(3) # Build cython module for python3 if python3 is found
-  if((NOT ${PYTHON2_FOUND}) AND (NOT ${PYTHON3_FOUND}))
+  if(NOT ${PYTHON3_FOUND})
     message(FATAL_ERROR "No python interpreter found to build cython modules")
   endif()
 endif()

amalgamation/python/mxnet_predict.py

@@ -55,46 +55,26 @@
 
 __all__ = ["Predictor", "load_ndarray_file"]
 
-if sys.version_info[0] == 3:
-    py_str = lambda x: x.decode('utf-8')
 
-    def c_str_array(strings):
-        """Create ctypes const char ** from a list of Python strings.
+py_str = lambda x: x.decode('utf-8')
 
-        Parameters
-        ----------
-        strings : list of string
-            Python strings.
 
-        Returns
-        -------
-        (ctypes.c_char_p * len(strings))
-            A const char ** pointer that can be passed to C API.
-        """
-        arr = (ctypes.c_char_p * len(strings))()
-        arr[:] = [s.encode('utf-8') for s in strings]
-        return arr
+def c_str_array(strings):
+    """Create ctypes const char ** from a list of Python strings.
 
+    Parameters
+    ----------
+    strings : list of string
+        Python strings.
 
-else:
-    py_str = lambda x: x
-
-    def c_str_array(strings):
-        """Create ctypes const char ** from a list of Python strings.
-
-        Parameters
-        ----------
-        strings : list of strings
-            Python strings.
-
-        Returns
-        -------
-        (ctypes.c_char_p * len(strings))
-            A const char ** pointer that can be passed to C API.
-        """
-        arr = (ctypes.c_char_p * len(strings))()
-        arr[:] = strings
-        return arr
+    Returns
+    -------
+    (ctypes.c_char_p * len(strings))
+        A const char ** pointer that can be passed to C API.
+    """
+    arr = (ctypes.c_char_p * len(strings))()
+    arr[:] = [s.encode('utf-8') for s in strings]
+    return arr
 
 
 def c_str(string):

ci/docker/runtime_functions.sh

@@ -43,11 +43,10 @@ scala_prepare() {
 
 check_cython() {
     set -ex
-    local python_ver=$1
-    local is_cython_used=$(python${python_ver} <<EOF
+    local is_cython_used=$(python3 <<EOF
 import sys
 import mxnet as mx
-cython_ndarraybase = 'mxnet._cy' + str(sys.version_info.major) + '.ndarray'
+cython_ndarraybase = 'mxnet._cy3.ndarray'
 print(mx.nd._internal.NDArrayBase.__module__ == cython_ndarraybase)
 EOF
 )
@@ -1080,7 +1079,7 @@ unittest_ubuntu_python3_gpu_cython() {
     export MXNET_ENABLE_CYTHON=1
     export MXNET_ENFORCE_CYTHON=1
     export DMLC_LOG_STACK_TRACE_DEPTH=10
-    check_cython 3
+    check_cython
     nosetests-3.4 $NOSE_COVERAGE_ARGUMENTS $NOSE_TIMER_ARGUMENTS --with-xunit --xunit-file nosetests_gpu.xml --verbose tests/python/gpu
 }
 

ci/jenkins/Jenkins_steps.groovy

@@ -24,23 +24,23 @@ utils = load('ci/Jenkinsfile_utils.groovy')
 
 // mxnet libraries
 mx_lib = 'lib/libmxnet.so, lib/libmxnet.a, lib/libtvm_runtime.so, lib/libtvmop.so, lib/tvmop.conf, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a'
-mx_lib_cython = 'lib/libmxnet.so, lib/libmxnet.a, lib/libtvm_runtime.so, lib/libtvmop.so, lib/tvmop.conf, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a, python/mxnet/_cy2/*.so, python/mxnet/_cy3/*.so'
+mx_lib_cython = 'lib/libmxnet.so, lib/libmxnet.a, lib/libtvm_runtime.so, lib/libtvmop.so, lib/tvmop.conf, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a, python/mxnet/_cy3/*.so'
 
 // Python wheels
 mx_pip = 'build/*.whl'
 
 // mxnet cmake libraries, in cmake builds we do not produce a libnvvm static library by default.
 mx_cmake_lib = 'build/libmxnet.so, build/libmxnet.a, build/3rdparty/tvm/libtvm_runtime.so, build/libtvmop.so, build/tvmop.conf, build/3rdparty/dmlc-core/libdmlc.a, build/tests/mxnet_unit_tests, build/3rdparty/openmp/runtime/src/libomp.so'
 mx_cmake_lib_no_tvm_op = 'build/libmxnet.so, build/libmxnet.a, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, build/3rdparty/dmlc-core/libdmlc.a, build/tests/mxnet_unit_tests, build/3rdparty/openmp/runtime/src/libomp.so'
-mx_cmake_lib_cython = 'build/libmxnet.so, build/libmxnet.a, build/3rdparty/tvm/libtvm_runtime.so, build/libtvmop.so, build/tvmop.conf, build/3rdparty/dmlc-core/libdmlc.a, build/tests/mxnet_unit_tests, build/3rdparty/openmp/runtime/src/libomp.so, python/mxnet/_cy2/*.so, python/mxnet/_cy3/*.so'
+mx_cmake_lib_cython = 'build/libmxnet.so, build/libmxnet.a, build/3rdparty/tvm/libtvm_runtime.so, build/libtvmop.so, build/tvmop.conf, build/3rdparty/dmlc-core/libdmlc.a, build/tests/mxnet_unit_tests, build/3rdparty/openmp/runtime/src/libomp.so, python/mxnet/_cy3/*.so'
 // mxnet cmake libraries, in cmake builds we do not produce a libnvvm static library by default.
 mx_cmake_lib_debug = 'build/libmxnet.so, build/libmxnet.a, build/3rdparty/tvm/libtvm_runtime.so, build/libtvmop.so, build/tvmop.conf, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, build/3rdparty/dmlc-core/libdmlc.a, build/tests/mxnet_unit_tests'
 mx_cmake_mkldnn_lib = 'build/libmxnet.so, build/libmxnet.a, build/3rdparty/tvm/libtvm_runtime.so, build/libtvmop.so, build/tvmop.conf, build/3rdparty/dmlc-core/libdmlc.a, build/tests/mxnet_unit_tests, build/3rdparty/openmp/runtime/src/libomp.so'
 mx_mkldnn_lib = 'lib/libmxnet.so, lib/libmxnet.a, lib/libtvm_runtime.so, lib/libtvmop.so, lib/tvmop.conf, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a'
 mx_tensorrt_lib = 'build/libmxnet.so, build/3rdparty/tvm/libtvm_runtime.so, build/libtvmop.so, build/tvmop.conf, lib/libnvonnxparser_runtime.so.0, lib/libnvonnxparser.so.0, lib/libonnx_proto.so, lib/libonnx.so'
-mx_lib_cpp_examples = 'lib/libmxnet.so, lib/libmxnet.a, lib/libtvm_runtime.so, lib/libtvmop.so, lib/tvmop.conf, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a, 3rdparty/ps-lite/build/libps.a, deps/lib/libprotobuf-lite.a, deps/lib/libzmq.a, build/cpp-package/example/*, python/mxnet/_cy2/*.so, python/mxnet/_cy3/*.so'
-mx_lib_cpp_capi = 'lib/libmxnet.so, lib/libmxnet.a, lib/libtvm_runtime.so, lib/libtvmop.so, lib/tvmop.conf, libsample_lib.so, lib/libmkldnn.so.1, lib/libmklml_intel.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a, 3rdparty/ps-lite/build/libps.a, deps/lib/libprotobuf-lite.a, deps/lib/libzmq.a, build/cpp-package/example/*, python/mxnet/_cy2/*.so, python/mxnet/_cy3/*.so, build/tests/cpp/mxnet_unit_tests'
-mx_lib_cpp_examples_no_tvm_op = 'lib/libmxnet.so, lib/libmxnet.a, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a, 3rdparty/ps-lite/build/libps.a, deps/lib/libprotobuf-lite.a, deps/lib/libzmq.a, build/cpp-package/example/*, python/mxnet/_cy2/*.so, python/mxnet/_cy3/*.so'
+mx_lib_cpp_examples = 'lib/libmxnet.so, lib/libmxnet.a, lib/libtvm_runtime.so, lib/libtvmop.so, lib/tvmop.conf, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a, 3rdparty/ps-lite/build/libps.a, deps/lib/libprotobuf-lite.a, deps/lib/libzmq.a, build/cpp-package/example/*, python/mxnet/_cy3/*.so'
+mx_lib_cpp_capi = 'lib/libmxnet.so, lib/libmxnet.a, lib/libtvm_runtime.so, lib/libtvmop.so, lib/tvmop.conf, libsample_lib.so, lib/libmkldnn.so.1, lib/libmklml_intel.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a, 3rdparty/ps-lite/build/libps.a, deps/lib/libprotobuf-lite.a, deps/lib/libzmq.a, build/cpp-package/example/*, python/mxnet/_cy3/*.so, build/tests/cpp/mxnet_unit_tests'
+mx_lib_cpp_examples_no_tvm_op = 'lib/libmxnet.so, lib/libmxnet.a, build/libcustomop_lib.so, build/libcustomop_gpu_lib.so, build/libsubgraph_lib.so, 3rdparty/dmlc-core/libdmlc.a, 3rdparty/tvm/nnvm/lib/libnnvm.a, 3rdparty/ps-lite/build/libps.a, deps/lib/libprotobuf-lite.a, deps/lib/libzmq.a, build/cpp-package/example/*, python/mxnet/_cy3/*.so'
 mx_lib_cpp_examples_cpu = 'build/libmxnet.so, build/3rdparty/tvm/libtvm_runtime.so, build/libtvmop.so, build/tvmop.conf, build/cpp-package/example/*'
 
 // Python unittest for CPU

docs/python_docs/python/tutorials/packages/gluon/text/gnmt.rst

@@ -35,7 +35,6 @@ Load MXNET and Gluon
     import time
     import random
     import os
-    import io
     import logging
     import numpy as np
     import mxnet as mx
@@ -226,11 +225,11 @@ EOS tokens to target sentence.
     data_val_lengths = get_data_lengths(data_val)
     data_test_lengths = get_data_lengths(data_test)
 
-    with io.open(os.path.join(save_dir, 'val_gt.txt'), 'w', encoding='utf-8') as of:
+    with open(os.path.join(save_dir, 'val_gt.txt'), 'w', encoding='utf-8') as of:
         for ele in val_tgt_sentences:
             of.write(' '.join(ele) + '\n')
 
-    with io.open(os.path.join(save_dir, 'test_gt.txt'), 'w', encoding='utf-8') as of:
+    with open(os.path.join(save_dir, 'test_gt.txt'), 'w', encoding='utf-8') as of:
         for ele in test_tgt_sentences:
             of.write(' '.join(ele) + '\n')
 
@@ -391,7 +390,7 @@ testing datasets.
 
 
     def write_sentences(sentences, file_path):
-        with io.open(file_path, 'w', encoding='utf-8') as of:
+        with open(file_path, 'w', encoding='utf-8') as of:
             for sent in sentences:
                 of.write(' '.join(sent) + '\n')
 

python/mxnet/__init__.py

@@ -19,7 +19,6 @@
 
 # coding: utf-8
 """MXNet: a concise, fast and flexible framework for deep learning."""
-from __future__ import absolute_import
 
 from .context import Context, current_context, cpu, gpu, cpu_pinned
 from . import engine, error

python/mxnet/_ctypes/ndarray.py

@@ -19,7 +19,6 @@
 # pylint: disable=invalid-name, protected-access, too-many-arguments
 # pylint: disable=global-statement, unused-import
 """NDArray configuration API."""
-from __future__ import absolute_import as _abs
 
 import ctypes
 

python/mxnet/_ctypes/symbol.py

@@ -18,7 +18,6 @@
 # coding: utf-8
 # pylint: disable=invalid-name, protected-access, too-many-arguments,  global-statement
 """Symbolic configuration API."""
-from __future__ import absolute_import as _abs
 
 import ctypes
 from ..base import _LIB

python/mxnet/attribute.py

@@ -17,7 +17,6 @@
 
 # coding: utf-8
 """Attribute scoping support for symbolic API."""
-from __future__ import absolute_import
 import threading
 import warnings
 from collections import defaultdict

python/mxnet/autograd.py

@@ -17,8 +17,6 @@
 
 # coding: utf-8
 """Autograd for NDArray."""
-from __future__ import absolute_import
-from __future__ import division
 
 from array import array
 from threading import Lock

python/mxnet/base.py

@@ -18,9 +18,7 @@
 # coding: utf-8
 # pylint: disable=invalid-name, no-member, trailing-comma-tuple, bad-mcs-classmethod-argument, unnecessary-pass, too-many-lines, wrong-import-position
 """ctypes library of mxnet and helper functions."""
-from __future__ import absolute_import
 
-import io
 import re
 import atexit
 import ctypes
@@ -51,12 +49,9 @@
 string_types = basestring,
 error_types = {}
 
-if sys.version_info[0] > 2:
-    # this function is needed for python3
-    # to convert ctypes.char_p .value back to python str
-    py_str = lambda x: x.decode('utf-8')
-else:
-    py_str = lambda x: x
+# this function is needed for python3
+# to convert ctypes.char_p .value back to python str
+py_str = lambda x: x.decode('utf-8')
 
 
 def data_dir_default():
@@ -78,28 +73,6 @@ def data_dir():
     """
     return os.getenv('MXNET_HOME', data_dir_default())
 
-class _Py2CompatibleUnicodeFileWriter(object):
-    """
-    Wraps a file handle decorating the write command to unicode the content before writing.
-    This makes writing files opened with encoding='utf-8' compatible with Python 2
-    """
-
-    def __init__(self, file_handle):
-        self._file_handle = file_handle
-        if sys.version_info[0] > 2:
-            self.unicode = str
-        else:
-            from functools import partial
-            # pylint: disable=undefined-variable
-            self.unicode = partial(unicode, encoding="utf-8")
-            # pylint: enable=undefined-variable
-
-    def write(self, value):
-        self._file_handle.write(self.unicode(value))
-
-    def __getattr__(self, name):
-        return getattr(self._file_handle, name)
-
 
 class _NullType(object):
     """Placeholder for arguments"""
@@ -404,83 +377,43 @@ def _load_lib():
 #----------------------------
 # helper function definition
 #----------------------------
-if sys.version_info[0] < 3:
-    def c_str(string):
-        """Create ctypes char * from a Python string.
-
-        Parameters
-        ----------
-        string : string type
-            Python string.
-
-        Returns
-        -------
-        str : c_char_p
-            A char pointer that can be passed to C API.
-
-        Examples
-        --------
-        >>> x = mx.base.c_str("Hello, World")
-        >>> print x.value
-        Hello, World
-        """
-        return ctypes.c_char_p(string)
+def c_str(string):
+    """Create ctypes char * from a Python string.
 
-    def c_str_array(strings):
-        """Create ctypes const char ** from a list of Python strings.
+    Parameters
+    ----------
+    string : string type
+        Python string.
 
-        Parameters
-        ----------
-        strings : list of string
-            Python strings.
+    Returns
+    -------
+    str : c_char_p
+        A char pointer that can be passed to C API.
 
-        Returns
-        -------
-        (ctypes.c_char_p * len(strings))
-            A const char ** pointer that can be passed to C API.
-        """
-        arr = (ctypes.c_char_p * len(strings))()
-        arr[:] = strings
-        return arr
-
-else:
-    def c_str(string):
-        """Create ctypes char * from a Python string.
-
-        Parameters
-        ----------
-        string : string type
-            Python string.
-
-        Returns
-        -------
-        str : c_char_p
-            A char pointer that can be passed to C API.
-
-        Examples
-        --------
-        >>> x = mx.base.c_str("Hello, World")
-        >>> print(x.value)
-        b"Hello, World"
-        """
-        return ctypes.c_char_p(string.encode('utf-8'))
+    Examples
+    --------
+    >>> x = mx.base.c_str("Hello, World")
+    >>> print(x.value)
+    b"Hello, World"
+    """
+    return ctypes.c_char_p(string.encode('utf-8'))
 
-    def c_str_array(strings):
-        """Create ctypes const char ** from a list of Python strings.
+def c_str_array(strings):
+    """Create ctypes const char ** from a list of Python strings.
 
-        Parameters
-        ----------
-        strings : list of string
-            Python strings.
+    Parameters
+    ----------
+    strings : list of string
+        Python strings.
 
-        Returns
-        -------
-        (ctypes.c_char_p * len(strings))
-            A const char ** pointer that can be passed to C API.
-        """
-        arr = (ctypes.c_char_p * len(strings))()
-        arr[:] = [s.encode('utf-8') for s in strings]
-        return arr
+    Returns
+    -------
+    (ctypes.c_char_p * len(strings))
+        A const char ** pointer that can be passed to C API.
+    """
+    arr = (ctypes.c_char_p * len(strings))()
+    arr[:] = [s.encode('utf-8') for s in strings]
+    return arr
 
 
 def c_array(ctype, values):
@@ -821,7 +754,7 @@ def get_module_file(module_name):
         module_path = module_name.split('.')
         module_path[-1] = 'gen_' + module_path[-1]
         file_name = os.path.join(path, '..', *module_path) + '.py'
-        module_file = _Py2CompatibleUnicodeFileWriter(io.open(file_name, 'w', encoding="utf-8"))
+        module_file = open(file_name, 'w', encoding="utf-8")
         dependencies = {'symbol': ['from ._internal import SymbolBase',
                                    'from ..base import _Null'],
                         'ndarray': ['from ._internal import NDArrayBase',