From 86050cd5dad0a1df8514a5aa980359ad86879bd2 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Fri, 23 Jun 2017 10:16:32 -0500
Subject: [PATCH 01/14] Delay matplotlib import

---
 pandas/plotting/__init__.py |  6 ------
 pandas/plotting/_core.py    | 22 ++++++++++++++++------
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/pandas/plotting/__init__.py b/pandas/plotting/__init__.py
index c3cbedb0fc28c..8f98e297e3e66 100644
--- a/pandas/plotting/__init__.py
+++ b/pandas/plotting/__init__.py
@@ -4,12 +4,6 @@
 
 # flake8: noqa
 
-try:  # mpl optional
-    from pandas.plotting import _converter
-    _converter.register()  # needs to override so set_xlim works with str/number
-except ImportError:
-    pass
-
 from pandas.plotting._misc import (scatter_matrix, radviz,
                                    andrews_curves, bootstrap_plot,
                                    parallel_coordinates, lag_plot,
diff --git a/pandas/plotting/_core.py b/pandas/plotting/_core.py
index aa919d600ec52..8ced50c7df696 100644
--- a/pandas/plotting/_core.py
+++ b/pandas/plotting/_core.py
@@ -40,12 +40,7 @@
                                     _get_xlim, _set_ticks_props,
                                     format_date_labels)
 
-
-if _mpl_ge_1_5_0():
-    # Compat with mp 1.5, which uses cycler.
-    import cycler
-    colors = mpl_stylesheet.pop('axes.color_cycle')
-    mpl_stylesheet['axes.prop_cycle'] = cycler.cycler('color', colors)
+_registered = False
 
 
 def _get_standard_kind(kind):
@@ -95,6 +90,7 @@ def __init__(self, data, kind=None, by=None, subplots=False, sharex=None,
                  secondary_y=False, colormap=None,
                  table=False, layout=None, **kwds):
 
+        self._setup()
         self.data = data
         self.by = by
 
@@ -178,6 +174,20 @@ def __init__(self, data, kind=None, by=None, subplots=False, sharex=None,
 
         self._validate_color_args()
 
+    def _setup(self):
+        global _registered
+        if not _registered:
+            from pandas.plotting import _converter
+            _converter.register()
+
+            if _mpl_ge_1_5_0():
+                # Compat with mp 1.5, which uses cycler.
+                import cycler
+                colors = mpl_stylesheet.pop('axes.color_cycle')
+                mpl_stylesheet['axes.prop_cycle'] = cycler.cycler('color', colors)
+
+            _registered = True
+
     def _validate_color_args(self):
         if 'color' not in self.kwds and 'colors' in self.kwds:
             warnings.warn(("'colors' is being deprecated. Please use 'color'"

From be3d13eeb923be9718e7de7b26b24e0df51d2bb4 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Wed, 27 Sep 2017 12:41:57 -0500
Subject: [PATCH 02/14] delay pytest

---
 pandas/util/_tester.py | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/pandas/util/_tester.py b/pandas/util/_tester.py
index aeb4259a9edae..d18467f17ec5b 100644
--- a/pandas/util/_tester.py
+++ b/pandas/util/_tester.py
@@ -7,21 +7,19 @@
 PKG = os.path.dirname(os.path.dirname(__file__))
 
 
-try:
-    import pytest
-except ImportError:
-    def test():
+def test(extra_args=None):
+    try:
+        import pytest
+    except ImportError:
         raise ImportError("Need pytest>=3.0 to run tests")
-else:
-    def test(extra_args=None):
-        cmd = ['--skip-slow', '--skip-network']
-        if extra_args:
-            if not isinstance(extra_args, list):
-                extra_args = [extra_args]
-            cmd = extra_args
-        cmd += [PKG]
-        print("running: pytest {}".format(' '.join(cmd)))
-        sys.exit(pytest.main(cmd))
+    cmd = ['--skip-slow', '--skip-network']
+    if extra_args:
+        if not isinstance(extra_args, list):
+            extra_args = [extra_args]
+        cmd = extra_args
+    cmd += [PKG]
+    print("running: pytest {}".format(' '.join(cmd)))
+    sys.exit(pytest.main(cmd))
 
 
 __all__ = ['test']

From cd2226c0018d06580771050d8dd9e737ec198799 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Wed, 27 Sep 2017 13:27:56 -0500
Subject: [PATCH 03/14] Delay excel, probably broken

---
 pandas/core/config_init.py | 24 +++++++++++++++++-------
 pandas/io/common.py        | 12 +++++-------
 pandas/io/excel.py         |  4 +++-
 3 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/pandas/core/config_init.py b/pandas/core/config_init.py
index 5652424a8f75b..09e80cb7bdee3 100644
--- a/pandas/core/config_init.py
+++ b/pandas/core/config_init.py
@@ -458,13 +458,23 @@ def _register_xlsx(engine, other):
                                        others=others)
         cf.register_option('xlsx.writer', engine, doc, validator=str)
 
-    try:
-        # better memory footprint
-        import xlsxwriter  # noqa
-        _register_xlsx('xlsxwriter', 'openpyxl')
-    except ImportError:
-        # fallback
-        _register_xlsx('openpyxl', 'xlsxwriter')
+_excel_registered = False
+
+
+def _register_excel_engines():
+    global _excel_registered
+
+    if not _excel_registered:
+        with cf.config_prefix('io.excel'):
+            try:
+                # better memory footprint
+                import xlsxwriter  # noqa
+                _register_xlsx('xlsxwriter', 'openpyxl')
+            except ImportError:
+                # fallback
+                _register_xlsx('openpyxl', 'xlsxwriter')
+        _excel_registered = True
+
 
 # Set up the io.parquet specific configuration.
 parquet_engine_doc = """
diff --git a/pandas/io/common.py b/pandas/io/common.py
index 69a7e69ea724b..3f04d34d37186 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -19,13 +19,6 @@
 # gh-12665: Alias for now and remove later.
 CParserError = ParserError
 
-
-try:
-    from s3fs import S3File
-    need_text_wrapping = (BytesIO, S3File)
-except ImportError:
-    need_text_wrapping = (BytesIO,)
-
 # common NA values
 # no longer excluding inf representations
 # '1.#INF','-1.#INF', '1.#INF000000',
@@ -322,6 +315,11 @@ def _get_handle(path_or_buf, mode, encoding=None, compression=None,
     handles : list of file-like objects
         A list of file-like object that were openned in this function.
     """
+    try:
+        from s3fs import S3File
+        need_text_wrapping = (BytesIO, S3File)
+    except ImportError:
+        need_text_wrapping = (BytesIO,)
 
     handles = list()
     f = path_or_buf
diff --git a/pandas/io/excel.py b/pandas/io/excel.py
index afecd76c498ef..a7a3b64a95a48 100644
--- a/pandas/io/excel.py
+++ b/pandas/io/excel.py
@@ -25,7 +25,7 @@
 import pandas._libs.json as json
 from pandas.compat import (map, zip, reduce, range, lrange, u, add_metaclass,
                            string_types, OrderedDict)
-from pandas.core import config
+from pandas.core import config, config_init
 from pandas.io.formats.printing import pprint_thing
 import pandas.compat as compat
 import pandas.compat.openpyxl_compat as openpyxl_compat
@@ -690,6 +690,8 @@ class ExcelWriter(object):
     # ExcelWriter.
     def __new__(cls, path, engine=None, **kwargs):
         # only switch class if generic(ExcelWriter)
+        config_init._register_excel_engines()
+
         if issubclass(cls, ExcelWriter):
             if engine is None:
                 if isinstance(path, string_types):

From 95d96fc0a1e5c740838d8f8eda4989795e0f6561 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 28 Sep 2017 14:16:27 -0500
Subject: [PATCH 04/14] Matplotlib cleanup

---
 pandas/plotting/_core.py  |  9 +-----
 pandas/plotting/_style.py | 67 ---------------------------------------
 2 files changed, 1 insertion(+), 75 deletions(-)

diff --git a/pandas/plotting/_core.py b/pandas/plotting/_core.py
index 8ced50c7df696..54fa12781542d 100644
--- a/pandas/plotting/_core.py
+++ b/pandas/plotting/_core.py
@@ -33,7 +33,7 @@
 from pandas.plotting._compat import (_mpl_ge_1_3_1,
                                      _mpl_ge_1_5_0,
                                      _mpl_ge_2_0_0)
-from pandas.plotting._style import (mpl_stylesheet, plot_params,
+from pandas.plotting._style import (plot_params,
                                     _get_standard_colors)
 from pandas.plotting._tools import (_subplots, _flatten, table,
                                     _handle_shared_axes, _get_all_lines,
@@ -179,13 +179,6 @@ def _setup(self):
         if not _registered:
             from pandas.plotting import _converter
             _converter.register()
-
-            if _mpl_ge_1_5_0():
-                # Compat with mp 1.5, which uses cycler.
-                import cycler
-                colors = mpl_stylesheet.pop('axes.color_cycle')
-                mpl_stylesheet['axes.prop_cycle'] = cycler.cycler('color', colors)
-
             _registered = True
 
     def _validate_color_args(self):
diff --git a/pandas/plotting/_style.py b/pandas/plotting/_style.py
index 8cb4e30e0d91c..f1d53da5f1396 100644
--- a/pandas/plotting/_style.py
+++ b/pandas/plotting/_style.py
@@ -14,73 +14,6 @@
 from pandas.plotting._compat import _mpl_ge_2_0_0
 
 
-# Extracted from https://gist.github.com/huyng/816622
-# this is the rcParams set when setting display.with_mpl_style
-# to True.
-mpl_stylesheet = {
-    'axes.axisbelow': True,
-    'axes.color_cycle': ['#348ABD',
-                         '#7A68A6',
-                         '#A60628',
-                         '#467821',
-                         '#CF4457',
-                         '#188487',
-                         '#E24A33'],
-    'axes.edgecolor': '#bcbcbc',
-    'axes.facecolor': '#eeeeee',
-    'axes.grid': True,
-    'axes.labelcolor': '#555555',
-    'axes.labelsize': 'large',
-    'axes.linewidth': 1.0,
-    'axes.titlesize': 'x-large',
-    'figure.edgecolor': 'white',
-    'figure.facecolor': 'white',
-    'figure.figsize': (6.0, 4.0),
-    'figure.subplot.hspace': 0.5,
-    'font.family': 'monospace',
-    'font.monospace': ['Andale Mono',
-                       'Nimbus Mono L',
-                       'Courier New',
-                       'Courier',
-                       'Fixed',
-                       'Terminal',
-                       'monospace'],
-    'font.size': 10,
-    'interactive': True,
-    'keymap.all_axes': ['a'],
-    'keymap.back': ['left', 'c', 'backspace'],
-    'keymap.forward': ['right', 'v'],
-    'keymap.fullscreen': ['f'],
-    'keymap.grid': ['g'],
-    'keymap.home': ['h', 'r', 'home'],
-    'keymap.pan': ['p'],
-    'keymap.save': ['s'],
-    'keymap.xscale': ['L', 'k'],
-    'keymap.yscale': ['l'],
-    'keymap.zoom': ['o'],
-    'legend.fancybox': True,
-    'lines.antialiased': True,
-    'lines.linewidth': 1.0,
-    'patch.antialiased': True,
-    'patch.edgecolor': '#EEEEEE',
-    'patch.facecolor': '#348ABD',
-    'patch.linewidth': 0.5,
-    'toolbar': 'toolbar2',
-    'xtick.color': '#555555',
-    'xtick.direction': 'in',
-    'xtick.major.pad': 6.0,
-    'xtick.major.size': 0.0,
-    'xtick.minor.pad': 6.0,
-    'xtick.minor.size': 0.0,
-    'ytick.color': '#555555',
-    'ytick.direction': 'in',
-    'ytick.major.pad': 6.0,
-    'ytick.major.size': 0.0,
-    'ytick.minor.pad': 6.0,
-    'ytick.minor.size': 0.0
-}
-
-
 def _get_standard_colors(num_colors=None, colormap=None, color_type='default',
                          color=None):
     import matplotlib.pyplot as plt

From bede1f9ecc987c75215cfa1102b633816b0cd70f Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 28 Sep 2017 14:36:40 -0500
Subject: [PATCH 05/14] excel configuration

---
 pandas/core/config_init.py | 66 +++++++++++++++++---------------------
 pandas/io/excel.py         | 16 +++++++--
 2 files changed, 43 insertions(+), 39 deletions(-)

diff --git a/pandas/core/config_init.py b/pandas/core/config_init.py
index 09e80cb7bdee3..33531e80449d8 100644
--- a/pandas/core/config_init.py
+++ b/pandas/core/config_init.py
@@ -437,43 +437,35 @@ def use_inf_as_na_cb(key):
 writer_engine_doc = """
 : string
     The default Excel writer engine for '{ext}' files. Available options:
-    '{default}' (the default){others}.
-"""
-
-with cf.config_prefix('io.excel'):
-    # going forward, will be additional writers
-    for ext, options in [('xls', ['xlwt']), ('xlsm', ['openpyxl'])]:
-        default = options.pop(0)
-        if options:
-            options = " " + ", ".join(options)
-        else:
-            options = ""
-        doc = writer_engine_doc.format(ext=ext, default=default,
-                                       others=options)
-        cf.register_option(ext + '.writer', default, doc, validator=str)
-
-    def _register_xlsx(engine, other):
-        others = ", '{other}'".format(other=other)
-        doc = writer_engine_doc.format(ext='xlsx', default=engine,
-                                       others=others)
-        cf.register_option('xlsx.writer', engine, doc, validator=str)
-
-_excel_registered = False
-
-
-def _register_excel_engines():
-    global _excel_registered
-
-    if not _excel_registered:
-        with cf.config_prefix('io.excel'):
-            try:
-                # better memory footprint
-                import xlsxwriter  # noqa
-                _register_xlsx('xlsxwriter', 'openpyxl')
-            except ImportError:
-                # fallback
-                _register_xlsx('openpyxl', 'xlsxwriter')
-        _excel_registered = True
+    auto, {others}.
+"""
+
+_xls_options = ['xlwt']
+_xlsm_options = ['openpyxl']
+_xlsx_options = ['openpyxl', 'xlsxwriter']
+
+
+with cf.config_prefix("io.excel.xls"):
+    cf.register_option("writer", "auto",
+                       writer_engine_doc.format(
+                           ext='xls',
+                           others=', '.join(_xls_options)),
+                       validator=str)
+
+with cf.config_prefix("io.excel.xlsm"):
+    cf.register_option("writer", "auto",
+                       writer_engine_doc.format(
+                           ext='xlsm',
+                           others=', '.join(_xlsm_options)),
+                       validator=str)
+
+
+with cf.config_prefix("io.excel.xlsx"):
+    cf.register_option("writer", "auto",
+                       writer_engine_doc.format(
+                           ext='xlsx',
+                           others=', '.join(_xlsx_options)),
+                       validator=str)
 
 
 # Set up the io.parquet specific configuration.
diff --git a/pandas/io/excel.py b/pandas/io/excel.py
index a7a3b64a95a48..9bcd24c0b660d 100644
--- a/pandas/io/excel.py
+++ b/pandas/io/excel.py
@@ -170,6 +170,16 @@ def register_writer(klass):
             _writer_extensions.append(ext)
 
 
+def _get_default_writer(ext):
+    _default_writers = {'xlsx': 'openpyxl', 'xlsm': 'openpyxl', 'xls': 'xlwt'}
+    try:
+        import xlsxwriter  # noqa
+        _default_writers['xlsx'] = 'xlsxwriter'
+    except ImportError:
+        pass
+    return _default_writers[ext]
+
+
 def get_writer(engine_name):
     if engine_name == 'openpyxl':
         try:
@@ -690,10 +700,10 @@ class ExcelWriter(object):
     # ExcelWriter.
     def __new__(cls, path, engine=None, **kwargs):
         # only switch class if generic(ExcelWriter)
-        config_init._register_excel_engines()
 
         if issubclass(cls, ExcelWriter):
-            if engine is None:
+            if engine is None or (isinstance(engine, string_types) and
+                                  engine == 'auto'):
                 if isinstance(path, string_types):
                     ext = os.path.splitext(path)[-1][1:]
                 else:
@@ -702,6 +712,8 @@ def __new__(cls, path, engine=None, **kwargs):
                 try:
                     engine = config.get_option('io.excel.{ext}.writer'
                                                .format(ext=ext))
+                    if engine == 'auto':
+                        engine = _get_default_writer(ext)
                 except KeyError:
                     error = ValueError("No engine for filetype: '{ext}'"
                                        .format(ext=ext))

From a1a15bb64249c83364d5ce39f8d134071ddcb6a1 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 28 Sep 2017 15:55:00 -0500
Subject: [PATCH 06/14] PERF: delay numexpr

---
 pandas/core/computation/__init__.py     | 23 -----------------------
 pandas/core/computation/check.py        | 22 ++++++++++++++++++++++
 pandas/core/computation/eval.py         |  8 ++++++--
 pandas/core/computation/expressions.py  |  2 +-
 pandas/core/frame.py                    |  7 +++++--
 pandas/core/internals.py                |  3 ++-
 pandas/core/ops.py                      | 10 ++++++++--
 pandas/core/panel.py                    |  3 ++-
 pandas/tests/computation/test_compat.py |  4 ++--
 pandas/tests/frame/test_query_eval.py   |  2 +-
 pandas/util/testing.py                  |  8 +++++---
 11 files changed, 54 insertions(+), 38 deletions(-)
 create mode 100644 pandas/core/computation/check.py

diff --git a/pandas/core/computation/__init__.py b/pandas/core/computation/__init__.py
index e13faf890d1f8..e69de29bb2d1d 100644
--- a/pandas/core/computation/__init__.py
+++ b/pandas/core/computation/__init__.py
@@ -1,23 +0,0 @@
-
-import warnings
-from distutils.version import LooseVersion
-
-_NUMEXPR_INSTALLED = False
-_MIN_NUMEXPR_VERSION = "2.4.6"
-
-try:
-    import numexpr as ne
-    ver = ne.__version__
-    _NUMEXPR_INSTALLED = ver >= LooseVersion(_MIN_NUMEXPR_VERSION)
-
-    if not _NUMEXPR_INSTALLED:
-        warnings.warn(
-            "The installed version of numexpr {ver} is not supported "
-            "in pandas and will be not be used\nThe minimum supported "
-            "version is {min_ver}\n".format(
-                ver=ver, min_ver=_MIN_NUMEXPR_VERSION), UserWarning)
-
-except ImportError:  # pragma: no cover
-    pass
-
-__all__ = ['_NUMEXPR_INSTALLED']
diff --git a/pandas/core/computation/check.py b/pandas/core/computation/check.py
new file mode 100644
index 0000000000000..bb8cc74bad3c2
--- /dev/null
+++ b/pandas/core/computation/check.py
@@ -0,0 +1,22 @@
+import warnings
+from distutils.version import LooseVersion
+
+_NUMEXPR_INSTALLED = False
+_MIN_NUMEXPR_VERSION = "2.4.6"
+
+try:
+    import numexpr as ne
+    ver = ne.__version__
+    _NUMEXPR_INSTALLED = ver >= LooseVersion(_MIN_NUMEXPR_VERSION)
+
+    if not _NUMEXPR_INSTALLED:
+        warnings.warn(
+            "The installed version of numexpr {ver} is not supported "
+            "in pandas and will be not be used\nThe minimum supported "
+            "version is {min_ver}\n".format(
+                ver=ver, min_ver=_MIN_NUMEXPR_VERSION), UserWarning)
+
+except ImportError:  # pragma: no cover
+    pass
+
+__all__ = ['_NUMEXPR_INSTALLED']
diff --git a/pandas/core/computation/eval.py b/pandas/core/computation/eval.py
index d391764794c1c..a5df6aea055ab 100644
--- a/pandas/core/computation/eval.py
+++ b/pandas/core/computation/eval.py
@@ -5,8 +5,6 @@
 
 import tokenize
 from pandas.io.formats.printing import pprint_thing
-from pandas.core.computation import _NUMEXPR_INSTALLED
-from pandas.core.computation.expr import Expr, _parsers, tokenize_string
 from pandas.core.computation.scope import _ensure_scope
 from pandas.compat import string_types
 from pandas.core.computation.engines import _engines
@@ -32,6 +30,7 @@ def _check_engine(engine):
     string engine
 
     """
+    from pandas.core.computation.check import _NUMEXPR_INSTALLED
 
     if engine is None:
         if _NUMEXPR_INSTALLED:
@@ -69,6 +68,8 @@ def _check_parser(parser):
     KeyError
       * If an invalid parser is passed
     """
+    from pandas.core.computation.expr import _parsers
+
     if parser not in _parsers:
         raise KeyError('Invalid parser {parser!r} passed, valid parsers are'
                        ' {valid}'.format(parser=parser, valid=_parsers.keys()))
@@ -129,6 +130,8 @@ def _convert_expression(expr):
 
 
 def _check_for_locals(expr, stack_level, parser):
+    from pandas.core.computation.expr import tokenize_string
+
     at_top_of_stack = stack_level == 0
     not_pandas_parser = parser != 'pandas'
 
@@ -252,6 +255,7 @@ def eval(expr, parser='pandas', engine=None, truediv=True,
     pandas.DataFrame.query
     pandas.DataFrame.eval
     """
+    from pandas.core.computation.expr import Expr
 
     inplace = validate_bool_kwarg(inplace, "inplace")
 
diff --git a/pandas/core/computation/expressions.py b/pandas/core/computation/expressions.py
index 8ddc625887a51..2196fb5917a44 100644
--- a/pandas/core/computation/expressions.py
+++ b/pandas/core/computation/expressions.py
@@ -9,7 +9,7 @@
 import warnings
 import numpy as np
 from pandas.core.common import _values_from_object
-from pandas.core.computation import _NUMEXPR_INSTALLED
+from pandas.core.computation.check import _NUMEXPR_INSTALLED
 from pandas.core.config import get_option
 
 if _NUMEXPR_INSTALLED:
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 5d439f88bca15..01e83821d4524 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -76,9 +76,7 @@
                                    create_block_manager_from_blocks)
 from pandas.core.series import Series
 from pandas.core.categorical import Categorical
-import pandas.core.computation.expressions as expressions
 import pandas.core.algorithms as algorithms
-from pandas.core.computation.eval import eval as _eval
 from pandas.compat import (range, map, zip, lrange, lmap, lzip, StringIO, u,
                            OrderedDict, raise_with_traceback)
 from pandas import compat
@@ -2296,6 +2294,8 @@ def eval(self, expr, inplace=False, **kwargs):
         >>> df.eval('a + b')
         >>> df.eval('c = a + b')
         """
+        from pandas.core.computation.eval import eval as _eval
+
         inplace = validate_bool_kwarg(inplace, 'inplace')
         resolvers = kwargs.pop('resolvers', None)
         kwargs['level'] = kwargs.pop('level', 0) + 1
@@ -3840,6 +3840,7 @@ def _combine_const(self, other, func, raise_on_error=True, try_cast=True):
 
     def _compare_frame_evaluate(self, other, func, str_rep, try_cast=True):
 
+        import pandas.core.computation.expressions as expressions
         # unique
         if self.columns.is_unique:
 
@@ -3992,6 +3993,7 @@ def combine_first(self, other):
         -------
         combined : DataFrame
         """
+        import pandas.core.computation.expressions as expressions
 
         def combiner(x, y, needs_i8_conversion=False):
             x_values = x.values if hasattr(x, 'values') else x
@@ -4027,6 +4029,7 @@ def update(self, other, join='left', overwrite=True, filter_func=None,
             If True, will raise an error if the DataFrame and other both
             contain data in the same place.
         """
+        import pandas.core.computation.expressions as expressions
         # TODO: Support other joins
         if join != 'left':  # pragma: no cover
             raise NotImplementedError("Only left join is supported")
diff --git a/pandas/core/internals.py b/pandas/core/internals.py
index 9e348819ce5a3..12ac7a5fd9f20 100644
--- a/pandas/core/internals.py
+++ b/pandas/core/internals.py
@@ -66,7 +66,6 @@
 from pandas._libs.tslib import Timedelta
 from pandas._libs.lib import BlockPlacement
 
-import pandas.core.computation.expressions as expressions
 from pandas.util._decorators import cache_readonly
 from pandas.util._validators import validate_bool_kwarg
 from pandas import compat
@@ -1395,6 +1394,8 @@ def where(self, other, cond, align=True, raise_on_error=True,
         -------
         a new block(s), the result of the func
         """
+        import pandas.core.computation.expressions as expressions
+
         values = self.values
         orig_other = other
         if transpose:
diff --git a/pandas/core/ops.py b/pandas/core/ops.py
index d37acf48ed9c2..506b9267f32b4 100644
--- a/pandas/core/ops.py
+++ b/pandas/core/ops.py
@@ -16,7 +16,6 @@
 
 from pandas import compat
 from pandas.util._decorators import Appender
-import pandas.core.computation.expressions as expressions
 
 from pandas.compat import bind_method
 import pandas.core.missing as missing
@@ -668,8 +667,9 @@ def _arith_method_SERIES(op, name, str_rep, fill_zeros=None, default_axis=None,
     Wrapper function for Series arithmetic operations, to avoid
     code duplication.
     """
-
     def na_op(x, y):
+        import pandas.core.computation.expressions as expressions
+
         try:
             result = expressions.evaluate(op, str_rep, x, y,
                                           raise_on_error=True, **eval_kwargs)
@@ -1193,6 +1193,8 @@ def to_series(right):
 def _arith_method_FRAME(op, name, str_rep=None, default_axis='columns',
                         fill_zeros=None, **eval_kwargs):
     def na_op(x, y):
+        import pandas.core.computation.expressions as expressions
+
         try:
             result = expressions.evaluate(op, str_rep, x, y,
                                           raise_on_error=True, **eval_kwargs)
@@ -1349,6 +1351,8 @@ def _arith_method_PANEL(op, name, str_rep=None, fill_zeros=None,
     # copied from Series na_op above, but without unnecessary branch for
     # non-scalar
     def na_op(x, y):
+        import pandas.core.computation.expressions as expressions
+
         try:
             result = expressions.evaluate(op, str_rep, x, y,
                                           raise_on_error=True, **eval_kwargs)
@@ -1378,6 +1382,8 @@ def f(self, other):
 
 def _comp_method_PANEL(op, name, str_rep=None, masker=False):
     def na_op(x, y):
+        import pandas.core.computation.expressions as expressions
+
         try:
             result = expressions.evaluate(op, str_rep, x, y,
                                           raise_on_error=True)
diff --git a/pandas/core/panel.py b/pandas/core/panel.py
index a3e35492ad9af..68733a3a8b94e 100644
--- a/pandas/core/panel.py
+++ b/pandas/core/panel.py
@@ -15,7 +15,6 @@
     is_string_like, is_scalar)
 from pandas.core.dtypes.missing import notna
 
-import pandas.core.computation.expressions as expressions
 import pandas.core.common as com
 import pandas.core.ops as ops
 import pandas.core.missing as missing
@@ -1500,6 +1499,8 @@ def _add_aggregate_operations(cls, use_numexpr=True):
         def _panel_arith_method(op, name, str_rep=None, default_axis=None,
                                 fill_zeros=None, **eval_kwargs):
             def na_op(x, y):
+                import pandas.core.computation.expressions as expressions
+
                 try:
                     result = expressions.evaluate(op, str_rep, x, y,
                                                   raise_on_error=True,
diff --git a/pandas/tests/computation/test_compat.py b/pandas/tests/computation/test_compat.py
index ed569625177d3..af39ee9815313 100644
--- a/pandas/tests/computation/test_compat.py
+++ b/pandas/tests/computation/test_compat.py
@@ -5,13 +5,13 @@
 
 from pandas.core.computation.engines import _engines
 import pandas.core.computation.expr as expr
-from pandas.core.computation import _MIN_NUMEXPR_VERSION
+from pandas.core.computation.check import _MIN_NUMEXPR_VERSION
 
 
 def test_compat():
     # test we have compat with our version of nu
 
-    from pandas.core.computation import _NUMEXPR_INSTALLED
+    from pandas.core.computation.check import _NUMEXPR_INSTALLED
     try:
         import numexpr as ne
         ver = ne.__version__
diff --git a/pandas/tests/frame/test_query_eval.py b/pandas/tests/frame/test_query_eval.py
index f0f1a2df27e93..a6c36792ef074 100644
--- a/pandas/tests/frame/test_query_eval.py
+++ b/pandas/tests/frame/test_query_eval.py
@@ -17,7 +17,7 @@
                                  makeCustomDataframe as mkdf)
 
 import pandas.util.testing as tm
-from pandas.core.computation import _NUMEXPR_INSTALLED
+from pandas.core.computation.check import _NUMEXPR_INSTALLED
 
 from pandas.tests.frame.common import TestData
 
diff --git a/pandas/util/testing.py b/pandas/util/testing.py
index c5f73ca0e885b..202c9473eea12 100644
--- a/pandas/util/testing.py
+++ b/pandas/util/testing.py
@@ -41,8 +41,6 @@
     StringIO, PY3
 )
 
-from pandas.core.computation import expressions as expr
-
 from pandas import (bdate_range, CategoricalIndex, Categorical, IntervalIndex,
                     DatetimeIndex, TimedeltaIndex, PeriodIndex, RangeIndex,
                     Index, MultiIndex,
@@ -2660,7 +2658,11 @@ def __exit__(self, exc_type, exc_value, traceback):
 
 
 @contextmanager
-def use_numexpr(use, min_elements=expr._MIN_ELEMENTS):
+def use_numexpr(use, min_elements=None):
+    from pandas.core.computation import expressions as expr
+    if min_elements is None:
+        min_elements = expr._MIN_ELEMENTS
+
     olduse = expr._USE_NUMEXPR
     oldmin = expr._MIN_ELEMENTS
     expr.set_use_numexpr(use)

From 028bb8a7794fb7c9ed481c576a6fed0d490e55d8 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 28 Sep 2017 15:58:19 -0500
Subject: [PATCH 07/14] fixup! Matplotlib cleanup

---
 pandas/plotting/_core.py | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/pandas/plotting/_core.py b/pandas/plotting/_core.py
index 54fa12781542d..211d9777e7515 100644
--- a/pandas/plotting/_core.py
+++ b/pandas/plotting/_core.py
@@ -43,6 +43,15 @@
 _registered = False
 
 
+def _setup():
+    # delay the import of matplotlib until nescessary
+    global _registered
+    if not _registered:
+        from pandas.plotting import _converter
+        _converter.register()
+        _registered = True
+
+
 def _get_standard_kind(kind):
     return {'density': 'kde'}.get(kind, kind)
 
@@ -90,7 +99,7 @@ def __init__(self, data, kind=None, by=None, subplots=False, sharex=None,
                  secondary_y=False, colormap=None,
                  table=False, layout=None, **kwds):
 
-        self._setup()
+        _setup()
         self.data = data
         self.by = by
 
@@ -174,13 +183,6 @@ def __init__(self, data, kind=None, by=None, subplots=False, sharex=None,
 
         self._validate_color_args()
 
-    def _setup(self):
-        global _registered
-        if not _registered:
-            from pandas.plotting import _converter
-            _converter.register()
-            _registered = True
-
     def _validate_color_args(self):
         if 'color' not in self.kwds and 'colors' in self.kwds:
             warnings.warn(("'colors' is being deprecated. Please use 'color'"
@@ -2059,6 +2061,7 @@ def boxplot_frame(self, column=None, by=None, ax=None, fontsize=None, rot=0,
                   grid=True, figsize=None, layout=None,
                   return_type=None, **kwds):
     import matplotlib.pyplot as plt
+    _setup()
     ax = boxplot(self, column=column, by=by, ax=ax, fontsize=fontsize,
                  grid=grid, rot=rot, figsize=figsize, layout=layout,
                  return_type=return_type, **kwds)
@@ -2154,7 +2157,7 @@ def hist_frame(data, column=None, by=None, grid=True, xlabelsize=None,
     kwds : other plotting keyword arguments
         To be passed to hist function
     """
-
+    _setup()
     if by is not None:
         axes = grouped_hist(data, column=column, by=by, ax=ax, grid=grid,
                             figsize=figsize, sharex=sharex, sharey=sharey,
@@ -2351,6 +2354,7 @@ def boxplot_frame_groupby(grouped, subplots=True, column=None, fontsize=None,
     >>> grouped = df.unstack(level='lvl1').groupby(level=0, axis=1)
     >>> boxplot_frame_groupby(grouped, subplots=False)
     """
+    _setup()
     if subplots is True:
         naxes = len(grouped)
         fig, axes = _subplots(naxes=naxes, squeeze=False,

From 85f8baa18878ae4aff9f6182ed02486312924586 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 28 Sep 2017 16:27:27 -0500
Subject: [PATCH 08/14] PERF: delay import of py.path, Pathlib

---
 pandas/io/common.py | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/pandas/io/common.py b/pandas/io/common.py
index 3f04d34d37186..534c1e0671150 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -27,19 +27,6 @@
     'N/A', 'n/a', 'NA', '#NA', 'NULL', 'null', 'NaN', '-NaN', 'nan', '-nan', ''
 ])
 
-try:
-    import pathlib
-    _PATHLIB_INSTALLED = True
-except ImportError:
-    _PATHLIB_INSTALLED = False
-
-
-try:
-    from py.path import local as LocalPath
-    _PY_PATH_INSTALLED = True
-except:
-    _PY_PATH_INSTALLED = False
-
 
 if compat.PY3:
     from urllib.request import urlopen, pathname2url
@@ -160,6 +147,18 @@ def _stringify_path(filepath_or_buffer):
     Any other object is passed through unchanged, which includes bytes,
     strings, buffers, or anything else that's not even path-like.
     """
+    try:
+        import pathlib
+        _PATHLIB_INSTALLED = True
+    except ImportError:
+        _PATHLIB_INSTALLED = False
+
+    try:
+        from py.path import local as LocalPath
+        _PY_PATH_INSTALLED = True
+    except ImportError:
+        _PY_PATH_INSTALLED = False
+
     if hasattr(filepath_or_buffer, '__fspath__'):
         return filepath_or_buffer.__fspath__()
     if _PATHLIB_INSTALLED and isinstance(filepath_or_buffer, pathlib.Path):

From 748ea2d8aab440113e22e8abb5c9430b25b41b5c Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 28 Sep 2017 16:37:50 -0500
Subject: [PATCH 09/14] Add a script to test imports

---
 scripts/check_imports.py | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 scripts/check_imports.py

diff --git a/scripts/check_imports.py b/scripts/check_imports.py
new file mode 100644
index 0000000000000..982e6ff67dc4a
--- /dev/null
+++ b/scripts/check_imports.py
@@ -0,0 +1,27 @@
+"""
+Check that certain modules are not loaded by `import pandas`
+"""
+import sys
+
+
+blacklist = {
+    'matplotlib',
+    'numexpr',
+    'xlsxwriter',
+    'openpyxl',
+    'xlwt',
+    'numexpr',
+}
+
+
+def main():
+    import pandas  # noqa
+
+    modules = set(x.split('.')[0] for x in sys.modules)
+    imported = modules & blacklist
+    if modules & blacklist:
+        sys.exit("Imported {}".format(imported))
+
+
+if __name__ == '__main__':
+    main()

From 52295b85d87ad82273e9a60b00a0b4290167fa6f Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 28 Sep 2017 16:40:38 -0500
Subject: [PATCH 10/14] CI: Check for accidental imports

---
 .travis.yml                      |  2 ++
 {scripts => ci}/check_imports.py | 14 +++++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)
 rename {scripts => ci}/check_imports.py (76%)

diff --git a/.travis.yml b/.travis.yml
index 034e2a32bb75c..9a7e40237bbb4 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -121,6 +121,8 @@ script:
   - ci/script_single.sh
   - ci/script_multi.sh
   - ci/lint.sh
+  - echo "checking imports"
+  - python ci/check_imports.py
   - echo "script done"
 
 after_success:
diff --git a/scripts/check_imports.py b/ci/check_imports.py
similarity index 76%
rename from scripts/check_imports.py
rename to ci/check_imports.py
index 982e6ff67dc4a..cee13d70c0dce 100644
--- a/scripts/check_imports.py
+++ b/ci/check_imports.py
@@ -3,14 +3,22 @@
 """
 import sys
 
-
 blacklist = {
+    'bs4',
+    'html5lib',
+    'jinja2'
+    'lxml',
     'matplotlib',
     'numexpr',
-    'xlsxwriter',
     'openpyxl',
+    'py',
+    'pytest',
+    's3fs',
+    'scipy',
+    'tables',
+    'xlrd',
+    'xlsxwriter',
     'xlwt',
-    'numexpr',
 }
 
 

From 067b561e6c30af492d058d5ec93116b4e5acbe03 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 28 Sep 2017 16:59:08 -0500
Subject: [PATCH 11/14] whatsnew

---
 doc/source/whatsnew/v0.21.0.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v0.21.0.txt b/doc/source/whatsnew/v0.21.0.txt
index c8a0a6bff5cc7..ff2d6cffcd10d 100644
--- a/doc/source/whatsnew/v0.21.0.txt
+++ b/doc/source/whatsnew/v0.21.0.txt
@@ -164,6 +164,7 @@ Other Enhancements
 - :func:`read_excel` raises ``ImportError`` with a better message if ``xlrd`` is not installed. (:issue:`17613`)
 - :func:`read_json` now accepts a ``chunksize`` parameter that can be used when ``lines=True``. If ``chunksize`` is passed, read_json now returns an iterator which reads in ``chunksize`` lines with each iteration. (:issue:`17048`)
 - :meth:`DataFrame.assign` will preserve the original order of ``**kwargs`` for Python 3.6+ users instead of sorting the column names
+- Improved the import time of pandas by about 2.25x  (:issue:`16764`)
 
 
 .. _whatsnew_0210.api_breaking:

From b9f6a14e5c06097f4ba92432f24e298f9a5db74d Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Fri, 29 Sep 2017 06:03:55 -0500
Subject: [PATCH 12/14] Added release note

---
 doc/source/whatsnew/v0.21.0.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/doc/source/whatsnew/v0.21.0.txt b/doc/source/whatsnew/v0.21.0.txt
index ff2d6cffcd10d..6b968a3f1ae32 100644
--- a/doc/source/whatsnew/v0.21.0.txt
+++ b/doc/source/whatsnew/v0.21.0.txt
@@ -560,6 +560,8 @@ Other API Changes
 - :func:`to_datetime` when passed a tz-aware ``origin=`` kwarg will now raise a more informative ``ValueError`` rather than a ``TypeError`` (:issue:`16842`)
 - Renamed non-functional ``index`` to ``index_col`` in :func:`read_stata` to improve API consistency (:issue:`16342`)
 - Bug in :func:`DataFrame.drop` caused boolean labels ``False`` and ``True`` to be treated as labels 0 and 1 respectively when dropping indices from a numeric index. This will now raise a ValueError (:issue:`16877`)
+- Pandas no longer registers matplotlib converters on import. The converters
+  will be registered and used when the first plot is draw (:issue:`17710`)
 
 .. _whatsnew_0210.deprecations:
 

From 9bbd9c61f04e6125204a587b55599e699b8f6bd0 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Fri, 29 Sep 2017 10:38:16 -0500
Subject: [PATCH 13/14] Fix script call

---
 .travis.yml         | 2 +-
 ci/check_imports.py | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.travis.yml b/.travis.yml
index 9a7e40237bbb4..fe1a2950dbf08 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -122,7 +122,7 @@ script:
   - ci/script_multi.sh
   - ci/lint.sh
   - echo "checking imports"
-  - python ci/check_imports.py
+  - source activate pandas && python ci/check_imports.py
   - echo "script done"
 
 after_success:
diff --git a/ci/check_imports.py b/ci/check_imports.py
index cee13d70c0dce..a83436e7d258c 100644
--- a/ci/check_imports.py
+++ b/ci/check_imports.py
@@ -6,6 +6,7 @@
 blacklist = {
     'bs4',
     'html5lib',
+    'ipython',
     'jinja2'
     'lxml',
     'matplotlib',

From 9d0f74a73aa26f8ba7a6e59e797dfa3638272eb5 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Fri, 29 Sep 2017 12:12:16 -0500
Subject: [PATCH 14/14] pep8

---
 pandas/io/excel.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/io/excel.py b/pandas/io/excel.py
index 9bcd24c0b660d..41e3b5283a532 100644
--- a/pandas/io/excel.py
+++ b/pandas/io/excel.py
@@ -25,7 +25,7 @@
 import pandas._libs.json as json
 from pandas.compat import (map, zip, reduce, range, lrange, u, add_metaclass,
                            string_types, OrderedDict)
-from pandas.core import config, config_init
+from pandas.core import config
 from pandas.io.formats.printing import pprint_thing
 import pandas.compat as compat
 import pandas.compat.openpyxl_compat as openpyxl_compat