Merge pull request petl-developers#358 from alimanfoo/issue_323

resolves petl-developers#323 with documentation and extra test

petl/io/sources.py

@@ -197,6 +197,31 @@ def open(self, mode='r'):
 
 
 class MemorySource(object):
+    """Memory data source. E.g.::
+
+        >>> import petl as etl
+        >>> data = b'foo,bar\\na,1\\nb,2\\nc,2\\n'
+        >>> source = etl.MemorySource(data)
+        >>> tbl = etl.fromcsv(source)
+        >>> tbl
+        +-----+-----+
+        | foo | bar |
+        +=====+=====+
+        | 'a' | '1' |
+        +-----+-----+
+        | 'b' | '2' |
+        +-----+-----+
+        | 'c' | '2' |
+        +-----+-----+
+
+        >>> sink = etl.MemorySource()
+        >>> tbl.tojson(sink)
+        >>> sink.getvalue()
+        b'[{"foo": "a", "bar": "1"}, {"foo": "b", "bar": "2"}, {"foo": "c", "bar": "2"}]'
+
+    Also supports appending.
+
+    """
 
     def __init__(self, s=None):
         self.s = s

petl/test/io/test_sources.py

@@ -11,18 +11,18 @@
 
 from petl.test.helpers import ieq, eq_
 import petl as etl
-from petl.io.sources import StringSource, PopenSource, ZipSource, \
+from petl.io.sources import MemorySource, PopenSource, ZipSource, \
     StdoutSource, GzipSource, BZ2Source
 
 
-def test_stringsource():
+def test_memorysource():
     tbl1 = (('foo', 'bar'),
             ('a', '1'),
             ('b', '2'),
             ('c', '2'))
 
     # test writing to a string buffer
-    ss = StringSource()
+    ss = MemorySource()
     etl.tocsv(tbl1, ss)
     expect = "foo,bar\r\na,1\r\nb,2\r\nc,2\r\n"
     if not PY2:
@@ -31,7 +31,7 @@ def test_stringsource():
     eq_(expect, actual)
 
     # test reading from a string buffer
-    tbl2 = etl.fromcsv(StringSource(actual))
+    tbl2 = etl.fromcsv(MemorySource(actual))
     ieq(tbl1, tbl2)
     ieq(tbl1, tbl2)
 
@@ -44,6 +44,20 @@ def test_stringsource():
     eq_(expect, actual)
 
 
+def test_memorysource_2():
+
+    data = 'foo,bar\r\na,1\r\nb,2\r\nc,2\r\n'
+    if not PY2:
+        data = data.encode('ascii')
+    actual = etl.fromcsv(MemorySource(data))
+    expect = (('foo', 'bar'),
+              ('a', '1'),
+              ('b', '2'),
+              ('c', '2'))
+    ieq(expect, actual)
+    ieq(expect, actual)
+
+
 def test_popensource():
 
     expect = (('foo', 'bar'),)