Fix other functions to conform with PEP 479

Applies the same fix that was done for iterrowslice to other functions that may receive an empty (as in headerless) table as input.
#613

petl/io/csv_py2.py

@@ -112,7 +112,10 @@ def __iter__(self):
             it = iter(self.table)
 
             # deal with header row
-            hdr = next(it)
+            try:
+                hdr = next(it)
+            except StopIteration:
+                return
             if self.write_header:
                 writer.writerow(hdr)
             # N.B., always yield header, even if we don't write it

petl/io/csv_py3.py

@@ -20,15 +20,15 @@ def fromcsv_impl(source, **kwargs):
 class CSVView(Table):
 
     def __init__(self, source, encoding, errors, header, **csvargs):
-            self.source = source
-            self.encoding = encoding
-            self.errors = errors
-            self.csvargs = csvargs
-            self.header = header
+        self.source = source
+        self.encoding = encoding
+        self.errors = errors
+        self.csvargs = csvargs
+        self.header = header
 
     def __iter__(self):
         if self.header is not None:
-          yield tuple(self.header)
+            yield tuple(self.header)
         with self.source.open('rb') as buf:
             csvfile = io.TextIOWrapper(buf, encoding=self.encoding,
                                        errors=self.errors, newline='')
@@ -86,7 +86,10 @@ def __iter__(self):
             try:
                 writer = csv.writer(csvfile, **self.csvargs)
                 it = iter(self.table)
-                hdr = next(it)
+                try:
+                    hdr = next(it)
+                except StopIteration:
+                    return
                 if self.write_header:
                     writer.writerow(hdr)
                 yield tuple(hdr)

petl/io/html.py

@@ -75,7 +75,10 @@ def tohtml(table, source=None, encoding=None, errors='strict', caption=None,
             it = iter(table)
 
             # write header
-            hdr = next(it)
+            try:
+                hdr = next(it)
+            except StopIteration:
+                hdr = []
             _write_begin(f, hdr, lineterminator, caption, index_header,
                          truncate)
 
@@ -166,10 +169,13 @@ def __iter__(self):
                 it = iter(table)
 
                 # write header
-                hdr = next(it)
+                try:
+                    hdr = next(it)
+                    yield hdr
+                except StopIteration:
+                    hdr = []
                 _write_begin(f, hdr, lineterminator, caption, index_header,
                              truncate)
-                yield hdr
 
                 # write body
                 if tr_style and callable(tr_style):
@@ -193,16 +199,17 @@ def _write_begin(f, flds, lineterminator, caption, index_header, truncate):
     f.write("<table class='petl'>" + lineterminator)
     if caption is not None:
         f.write(('<caption>%s</caption>' % caption) + lineterminator)
-    f.write('<thead>' + lineterminator)
-    f.write('<tr>' + lineterminator)
-    for i, h in enumerate(flds):
-        if index_header:
-            h = '%s|%s' % (i, h)
-        if truncate:
-            h = h[:truncate]
-        f.write(('<th>%s</th>' % h) + lineterminator)
-    f.write('</tr>' + lineterminator)
-    f.write('</thead>' + lineterminator)
+    if flds:
+        f.write('<thead>' + lineterminator)
+        f.write('<tr>' + lineterminator)
+        for i, h in enumerate(flds):
+            if index_header:
+                h = '%s|%s' % (i, h)
+            if truncate:
+                h = h[:truncate]
+            f.write(('<th>%s</th>' % h) + lineterminator)
+        f.write('</tr>' + lineterminator)
+        f.write('</thead>' + lineterminator)
     f.write('<tbody>' + lineterminator)
 
 

petl/io/pandas.py

@@ -29,7 +29,10 @@ def todataframe(table, index=None, exclude=None, columns=None,
     """
     import pandas as pd
     it = iter(table)
-    header = next(it)
+    try:
+        header = next(it)
+    except StopIteration:
+        header = None  # Will create an Empty DataFrame
     if columns is None:
         columns = header
     return pd.DataFrame.from_records(it, index=index, exclude=exclude,

petl/io/pickle.py

@@ -119,7 +119,10 @@ def _writepickle(table, source, mode, protocol, write_header):
     source = write_source_from_arg(source, mode)
     with source.open(mode) as f:
         it = iter(table)
-        hdr = next(it)
+        try:
+            hdr = next(it)
+        except StopIteration:
+            return
         if write_header:
             pickle.dump(hdr, f, protocol)
         for row in it:
@@ -153,7 +156,10 @@ def __iter__(self):
         source = write_source_from_arg(self.source)
         with source.open('wb') as f:
             it = iter(self.table)
-            hdr = next(it)
+            try:
+                hdr = next(it)
+            except StopIteration:
+                return
             if self.write_header:
                 pickle.dump(hdr, f, protocol)
             yield tuple(hdr)

petl/io/text.py

@@ -194,7 +194,10 @@ def _writetext(table, source, mode, encoding, errors, template, prologue,
             if prologue is not None:
                 f.write(prologue)
             it = iter(table)
-            hdr = next(it)
+            try:
+                hdr = next(it)
+            except StopIteration:
+                hdr = []
             flds = list(map(text_type, hdr))
             for row in it:
                 rec = asdict(flds, row)
@@ -266,7 +269,10 @@ def _iterteetext(table, source, encoding, errors, template, prologue, epilogue):
             if prologue is not None:
                 f.write(prologue)
             it = iter(table)
-            hdr = next(it)
+            try:
+                hdr = next(it)
+            except StopIteration:
+                return
             yield tuple(hdr)
             flds = list(map(text_type, hdr))
             for row in it:

petl/io/xls.py

@@ -85,12 +85,15 @@ def toxls(tbl, filename, sheet, encoding=None, style_compression=0,
     else:
         # handle styles
         it = iter(tbl)
-        hdr = next(it)
-        flds = list(map(str, hdr))
-        for c, f in enumerate(flds):
-            ws.write(0, c, label=f)
-            if f not in styles or styles[f] is None:
-                styles[f] = xlwt.Style.default_style
+        try:
+            hdr = next(it)
+            flds = list(map(str, hdr))
+            for c, f in enumerate(flds):
+                ws.write(0, c, label=f)
+                if f not in styles or styles[f] is None:
+                    styles[f] = xlwt.Style.default_style
+        except StopIteration:
+            pass  # no header written
         # convert to list for easy zipping
         styles = [styles[f] for f in flds]
         for r, row in enumerate(it):

petl/io/xlsx.py

@@ -113,9 +113,12 @@ def toxlsx(tbl, filename, sheet=None, write_header=True, mode="replace"):
     ws = _insert_sheet_on_workbook(mode, sheet, wb)
     if write_header:
         it = iter(tbl)
-        hdr = next(it)
-        flds = list(map(text_type, hdr))
-        rows = itertools.chain([flds], it)
+        try:
+            hdr = next(it)
+            flds = list(map(text_type, hdr))
+            rows = itertools.chain([flds], it)
+        except StopIteration:
+            rows = it
     else:
         rows = data(tbl)
     for row in rows:
@@ -184,9 +187,12 @@ def appendxlsx(tbl, filename, sheet=None, write_header=False):
             ws = wb[str(sheet)]
         if write_header:
             it = iter(tbl)
-            hdr = next(it)
-            flds = list(map(text_type, hdr))
-            rows = itertools.chain([flds], it)
+            try:
+                hdr = next(it)
+                flds = list(map(text_type, hdr))
+                rows = itertools.chain([flds], it)
+            except StopIteration:
+                rows = it
         else:
             rows = data(tbl)
         for row in rows:

petl/test/helpers.py

@@ -10,7 +10,7 @@
 
 def eq_(expect, actual, msg=None):
     """Test when two values from a python variable are exactly equals (==)"""
-    assert expect == actual, msg
+    assert expect == actual, msg or ('%r != %s' % (expect, actual))
 
 
 def assert_almost_equal(first, second, places=None, msg=None):

petl/test/io/test_html.py

@@ -118,3 +118,21 @@ def test_tohtml_with_style():
             u"</table>\n"
         )
         eq_(expect, actual)
+
+
+def test_tohtml_headerless():
+    table = []
+
+    f = NamedTemporaryFile(delete=False)
+    tohtml(table, f.name, encoding='ascii', lineterminator='\n')
+
+    # check what it did
+    with io.open(f.name, mode='rt', encoding='ascii', newline='') as o:
+        actual = o.read()
+        expect = (
+            u"<table class='petl'>\n"
+            u"<tbody>\n"
+            u"</tbody>\n"
+            u"</table>\n"
+        )
+        eq_(expect, actual)

petl/test/io/test_pandas.py

@@ -26,6 +26,12 @@ def test_todataframe():
         actual = todataframe(tbl)
         assert expect.equals(actual)
 
+    def test_headerless():
+        tbl = []
+        expect = pd.DataFrame()
+        actual = todataframe(tbl)
+        assert expect.equals(actual)
+
     def test_fromdataframe():
         tbl = [('foo', 'bar', 'baz'),
                ('apples', 1, 2.5),

petl/test/io/test_pickle.py

@@ -10,6 +10,14 @@
 from petl.io.pickle import frompickle, topickle, appendpickle
 
 
+def picklereader(fl):
+    try:
+        while True:
+            yield pickle.load(fl)
+    except EOFError:
+        pass
+
+
 def test_frompickle():
 
     f = NamedTemporaryFile(delete=False)
@@ -36,13 +44,6 @@ def test_topickle_appendpickle():
     f = NamedTemporaryFile(delete=False)
     topickle(table, f.name)
 
-    def picklereader(fl):
-        try:
-            while True:
-                yield pickle.load(fl)
-        except EOFError:
-            pass
-
     # check what it did
     with open(f.name, 'rb') as o:
         actual = picklereader(o)
@@ -66,3 +67,12 @@ def picklereader(fl):
                   ('e', 9),
                   ('f', 1))
         ieq(expect, actual)
+
+
+def test_topickle_headerless():
+    table = []
+    f = NamedTemporaryFile(delete=False)
+    topickle(table, f.name)
+    expect = []
+    with open(f.name, 'rb') as o:
+        ieq(expect, picklereader(o))

petl/test/io/test_text.py

@@ -174,3 +174,18 @@ def test_totext_gz():
         eq_(expect, actual)
     finally:
         o.close()
+
+
+def test_totext_headerless():
+    table = []
+    f = NamedTemporaryFile(delete=False)
+    prologue = "-- START\n"
+    template = "+ {f1}\n"
+    epilogue = "-- END\n"
+    totext(table, f.name, encoding='ascii', template=template,
+           prologue=prologue, epilogue=epilogue)
+
+    with io.open(f.name, mode='rt', encoding='ascii', newline='') as o:
+        actual = o.read()
+        expect = prologue + epilogue
+        eq_(expect, actual)

petl/test/io/test_xls.py

@@ -85,6 +85,15 @@ def test_toxls():
         ieq(expect, actual)
         ieq(expect, actual)
 
+    def test_toxls_headerless():
+        expect = []
+        f = NamedTemporaryFile(delete=False)
+        f.close()
+        toxls(expect, f.name, 'Sheet1')
+        actual = fromxls(f.name, 'Sheet1')
+        ieq(expect, actual)
+        ieq(expect, actual)
+
     def test_toxls_date():
         expect = (('foo', 'bar'),
                   (u'é', datetime(2012, 1, 1)),
@@ -128,4 +137,4 @@ def wrapper(self, *args, **kwargs):
                       ('C', 2),
                       (u'é', datetime(2012, 1, 1)))
             ieq(expect, tbl)
-            ieq(expect, tbl)
+            ieq(expect, tbl)

petl/test/io/test_xlsx.py

@@ -226,3 +226,13 @@ def test_appendxlsx_with_non_str_header(xlsx_table_with_non_str_header, xlsx_tes
     appendxlsx(xlsx_table_with_non_str_header, f.name, 'Sheet1')
     expect = etl.cat(xlsx_test_table, xlsx_table_with_non_str_header)
     ieq(expect, actual)
+
+
+def test_toxlsx_headerless():
+    expect = []
+    f = NamedTemporaryFile(delete=False)
+    f.close()
+    toxlsx(expect, f.name)
+    actual = fromxlsx(f.name)
+    ieq(expect, actual)
+    ieq(expect, actual)