Implement Series.str.zfill() (#397)

* Implement Series.str.zfill()

* Minor change in tests for Series.str.zfill()

Author: densmirn

examples/series_str_zfill.py

@@ -0,0 +1,39 @@
+# *****************************************************************************
+# Copyright (c) 2019, Intel Corporation All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#     Redistributions of source code must retain the above copyright notice,
+#     this list of conditions and the following disclaimer.
+#
+#     Redistributions in binary form must reproduce the above copyright notice,
+#     this list of conditions and the following disclaimer in the documentation
+#     and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+# OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+# OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+# *****************************************************************************
+
+import pandas as pd
+from numba import njit
+
+
+@njit
+def series_str_zfill():
+    series = pd.Series(['dog', 'foo', 'bar'])  # Series of 'dog', 'foo', 'bar'
+    out_series = series.str.zfill(5)
+
+    return out_series  # Expect series of '00dog', '00foo', '00bar'
+
+
+print(series_str_zfill())

sdc/datatypes/hpat_pandas_stringmethods_functions.py

@@ -613,6 +613,72 @@ def hpat_pandas_stringmethods_startswith_impl(self, pat, na=None):
     return hpat_pandas_stringmethods_startswith_impl
 
 
+@overload_method(StringMethodsType, 'zfill')
+def hpat_pandas_stringmethods_zfill(self, width):
+    """
+    Intel Scalable Dataframe Compiler User Guide
+    ********************************************
+    Pandas API: pandas.Series.str.zfill
+
+    Examples
+    --------
+    .. literalinclude:: ../../../examples/series_str_zfill.py
+       :language: python
+       :lines: 27-
+       :caption: Pad strings in the Series by prepending '0' characters
+       :name: ex_series_str_zfill
+
+    .. code-block:: console
+
+        > python ./series_str_zfill.py
+        0    00dog
+        1    00foo
+        2    00bar
+        dtype: object
+
+    .. todo:: Add support of 32-bit Unicode for `str.zfill()`
+
+    Intel Scalable Dataframe Compiler Developer Guide
+    *************************************************
+
+    Pandas Series method :meth:`pandas.core.strings.StringMethods.zfill()` implementation.
+
+    Note: Unicode type of list elements are supported only. Numpy.NaN is not supported as elements.
+
+    .. only:: developer
+
+    Test: python -m sdc.runtests -k sdc.tests.test_series.TestSeries.test_series_zfill
+
+    Parameters
+    ----------
+    self: :class:`pandas.core.strings.StringMethods`
+        input arg
+    width: :obj:`int`
+        Minimum width of resulting string
+
+    Returns
+    -------
+    :obj:`pandas.Series`
+         returns :obj:`pandas.Series` object
+    """
+
+    ty_checker = TypeChecker('Method zfill().')
+    ty_checker.check(self, StringMethodsType)
+
+    if not isinstance(width, Integer):
+        ty_checker.raise_exc(width, 'int', 'width')
+
+    def hpat_pandas_stringmethods_zfill_impl(self, width):
+        item_count = len(self._data)
+        result = [''] * item_count
+        for idx, item in enumerate(self._data._data):
+            result[idx] = item.zfill(width)
+
+        return pandas.Series(result, self._data._index, name=self._data._name)
+
+    return hpat_pandas_stringmethods_zfill_impl
+
+
 def _hpat_pandas_stringmethods_autogen(method_name):
     """"
     The function generates a function for 'method_name' from source text that is created on the fly.

sdc/hiframes/pd_series_ext.py

@@ -760,7 +760,7 @@ def resolve_head(self, ary, args, kws):
 
 str2str_methods_excluded = [
     'upper', 'center', 'endswith', 'find', 'isupper', 'len', 'ljust',
-    'lower', 'lstrip', 'rjust', 'rstrip', 'startswith', 'strip'
+    'lower', 'lstrip', 'rjust', 'rstrip', 'startswith', 'strip', 'zfill'
 ]
 """
     Functions which are used from Numba directly by calling from StringMethodsType

sdc/tests/test_series.py

@@ -2692,6 +2692,37 @@ def test_impl(series, pat, na):
         msg = msg_tmpl.format('expected: None')
         self.assertIn(msg, str(raises.exception))
 
+    def test_series_str_zfill(self):
+        def test_impl(series, width):
+            return series.str.zfill(width)
+
+        hpat_func = self.jit(test_impl)
+
+        data = test_global_input_data_unicode_kind1
+        data_lengths = [len(s) for s in data]
+
+        for index in [None, list(range(len(data)))[::-1], data[::-1]]:
+            series = pd.Series(data, index, name='A')
+            for width in [max(data_lengths) + 5, min(data_lengths)]:
+                jit_result = hpat_func(series, width)
+                ref_result = test_impl(series, width)
+                pd.testing.assert_series_equal(jit_result, ref_result)
+
+    def test_series_str_zfill_exception_unsupported_kind4(self):
+        def test_impl(series, width):
+            return series.str.zfill(width)
+
+        hpat_func = self.jit(test_impl)
+
+        data = test_global_input_data_unicode_kind4
+        series = pd.Series(data)
+        width = max(len(s) for s in data) + 5
+
+        with self.assertRaises(SystemError) as raises:
+            hpat_func(series, width)
+        msg = 'NULL object passed to Py_BuildValue'
+        self.assertIn(msg, str(raises.exception))
+
     def test_series_str2str(self):
         common_methods = ['lower', 'upper', 'isupper']
         sdc_methods = ['capitalize', 'swapcase', 'title',