Tuning ValueHolder as I could not find better option to generate the double-underscore methods.

bonobo/config/configurables.py

@@ -74,9 +74,11 @@ class Configurable(metaclass=ConfigurableMeta):
         # transform positional arguments in keyword arguments if possible.
         position = 0
         for positional_option in self.__positional_options__:
+            if len(args) <= position:
+                break
+            kwargs[positional_option] = args[position]
+            position += 1
             if positional_option in missing:
-                kwargs[positional_option] = args[position]
-                position += 1
                 missing.remove(positional_option)
 
         # complain if there are still missing options.

bonobo/config/processors.py

@@ -1,11 +1,9 @@
-import functools
-
 import types
 from collections import Iterable
-
-from bonobo.util.compat import deprecated_alias, deprecated
+from contextlib import contextmanager
 
 from bonobo.config.options import Option
+from bonobo.util.compat import deprecated_alias
 from bonobo.util.iterators import ensure_tuple
 
 _CONTEXT_PROCESSORS_ATTR = '__processors__'
@@ -52,6 +50,14 @@ class ContextCurrifier:
         self._stack = []
         self._stack_values = []
 
+    def __iter__(self):
+        yield from self.wrapped
+
+    def __call__(self, *args, **kwargs):
+        if not callable(self.wrapped) and isinstance(self.wrapped, Iterable):
+            return self.__iter__()
+        return self.wrapped(*self.context, *args, **kwargs)
+
     def setup(self, *context):
         if len(self._stack):
             raise RuntimeError('Cannot setup context currification twice.')
@@ -63,14 +69,6 @@ class ContextCurrifier:
                 self.context += ensure_tuple(_append_to_context)
             self._stack.append(_processed)
 
-    def __iter__(self):
-        yield from self.wrapped
-
-    def __call__(self, *args, **kwargs):
-        if not callable(self.wrapped) and isinstance(self.wrapped, Iterable):
-            return self.__iter__()
-        return self.wrapped(*self.context, *args, **kwargs)
-
     def teardown(self):
         while len(self._stack):
             processor = self._stack.pop()
@@ -84,6 +82,23 @@ class ContextCurrifier:
                 # No error ? We should have had StopIteration ...
                 raise RuntimeError('Context processors should not yield more than once.')
 
+    @contextmanager
+    def as_contextmanager(self, *context):
+        """
+        Convenience method to use it as a contextmanager, mostly for test purposes.
+
+        Example:
+
+            >>> with ContextCurrifier(node).as_contextmanager(context) as stack:
+            ...     stack()
+
+        :param context:
+        :return:
+        """
+        self.setup(*context)
+        yield self
+        self.teardown()
+
 
 def resolve_processors(mixed):
     try:

bonobo/ext/opendatasoft.py

@@ -46,7 +46,7 @@ class OpenDataSoftAPI(Configurable):
             for row in records:
                 yield {**row.get('fields', {}), 'geometry': row.get('geometry', {})}
 
-            start.value += self.rows
+            start += self.rows
 
 
 __all__ = [

bonobo/nodes/basics.py

@@ -3,10 +3,12 @@ from pprint import pprint as _pprint
 
 from colorama import Fore, Style
 
+from bonobo.config import Configurable, Option
 from bonobo.config.processors import ContextProcessor
 from bonobo.structs.bags import Bag
 from bonobo.util.objects import ValueHolder
 from bonobo.util.term import CLEAR_EOL
+from bonobo.constants import NOT_MODIFIED
 
 __all__ = [
     'identity',
@@ -23,19 +25,26 @@ def identity(x):
     return x
 
 
-def Limit(n=10):
-    from bonobo.constants import NOT_MODIFIED
-    i = 0
+class Limit(Configurable):
+    """
+    Creates a Limit() node, that will only let go through the first n rows (defined by the `limit` option), unmodified.
 
-    def _limit(*args, **kwargs):
-        nonlocal i, n
-        i += 1
-        if i <= n:
+    .. attribute:: limit
+
+        Number of rows to let go through.
+
+    """
+    limit = Option(positional=True, default=10)
+
+    @ContextProcessor
+    def counter(self, context):
+        yield ValueHolder(0)
+
+    def call(self, counter, *args, **kwargs):
+        counter += 1
+        if counter <= self.limit:
             yield NOT_MODIFIED
 
-    _limit.__name__ = 'Limit({})'.format(n)
-    return _limit
-
 
 def Tee(f):
     from bonobo.constants import NOT_MODIFIED
@@ -57,7 +66,7 @@ def count(counter, *args, **kwargs):
 def _count_counter(self, context):
     counter = ValueHolder(0)
     yield counter
-    context.send(Bag(counter.value))
+    context.send(Bag(counter._value))
 
 
 pprint = Tee(_pprint)

bonobo/nodes/io/csv.py

@@ -46,8 +46,11 @@ class CsvReader(CsvHandler, FileReader):
 
     def read(self, fs, file, headers):
         reader = csv.reader(file, delimiter=self.delimiter, quotechar=self.quotechar)
-        headers.value = headers.value or next(reader)
-        field_count = len(headers.value)
+
+        if not headers.get():
+            headers.set(next(reader))
+
+        field_count = len(headers)
 
         if self.skip and self.skip > 0:
             for _ in range(0, self.skip):
@@ -68,9 +71,9 @@ class CsvWriter(CsvHandler, FileWriter):
         yield writer, headers
 
     def write(self, fs, file, lineno, writer, headers, row):
-        if not lineno.value:
-            headers.value = headers.value or row.keys()
-            writer.writerow(headers.value)
-        writer.writerow(row[header] for header in headers.value)
-        lineno.value += 1
+        if not lineno:
+            headers.set(headers.value or row.keys())
+            writer.writerow(headers.get())
+        writer.writerow(row[header] for header in headers.get())
+        lineno += 1
         return NOT_MODIFIED

bonobo/nodes/io/file.py

@@ -86,7 +86,7 @@ class FileWriter(Writer):
 
     @ContextProcessor
     def lineno(self, context, fs, file):
-        lineno = ValueHolder(0, type=int)
+        lineno = ValueHolder(0)
         yield lineno
 
     def write(self, fs, file, lineno, row):
@@ -94,7 +94,7 @@ class FileWriter(Writer):
         Write a row on the next line of opened file in context.
         """
         self._write_line(file, (self.eol if lineno.value else '') + row)
-        lineno.value += 1
+        lineno += 1
         return NOT_MODIFIED
 
     def _write_line(self, file, line):

bonobo/structs/bags.py

@@ -65,8 +65,10 @@ class Bag:
         if len(args) == 0 and len(kwargs) == 0:
             try:
                 iter(func_or_iter)
+
                 def generator():
                     yield from func_or_iter
+
                 return generator()
             except TypeError as exc:
                 raise TypeError('Could not apply bag to {}.'.format(func_or_iter)) from exc

bonobo/util/objects.py

@@ -1,3 +1,7 @@
+import functools
+from functools import partial
+
+
 def get_name(mixed):
     try:
         return mixed.__name__
@@ -27,181 +31,194 @@ class ValueHolder:
     
     """
 
-    def __init__(self, value, *, type=None):
-        self.value = value
-        self.type = type
+    def __init__(self, value):
+        self._value = value
 
-    def __repr__(self):
-        return repr(self.value)
+    @property
+    def value(self):
+        # XXX deprecated
+        return self._value
 
-    def __lt__(self, other):
-        return self.value < other
+    def get(self):
+        return self._value
 
-    def __le__(self, other):
-        return self.value <= other
+    def set(self, new_value):
+        self._value = new_value
+
+    def __bool__(self):
+        return bool(self._value)
 
     def __eq__(self, other):
-        return self.value == other
+        return self._value == other
 
     def __ne__(self, other):
-        return self.value != other
+        return self._value != other
+
+    def __repr__(self):
+        return repr(self._value)
+
+    def __lt__(self, other):
+        return self._value < other
+
+    def __le__(self, other):
+        return self._value <= other
 
     def __gt__(self, other):
-        return self.value > other
+        return self._value > other
 
     def __ge__(self, other):
-        return self.value >= other
+        return self._value >= other
 
     def __add__(self, other):
-        return self.value + other
+        return self._value + other
 
     def __radd__(self, other):
-        return other + self.value
+        return other + self._value
 
     def __iadd__(self, other):
-        self.value += other
+        self._value += other
         return self
 
     def __sub__(self, other):
-        return self.value - other
+        return self._value - other
 
     def __rsub__(self, other):
-        return other - self.value
+        return other - self._value
 
     def __isub__(self, other):
-        self.value -= other
+        self._value -= other
         return self
 
     def __mul__(self, other):
-        return self.value * other
+        return self._value * other
 
     def __rmul__(self, other):
-        return other * self.value
+        return other * self._value
 
     def __imul__(self, other):
-        self.value *= other
+        self._value *= other
         return self
 
     def __matmul__(self, other):
-        return self.value @ other
+        return self._value @ other
 
     def __rmatmul__(self, other):
-        return other @ self.value
+        return other @ self._value
 
     def __imatmul__(self, other):
-        self.value @= other
+        self._value @= other
         return self
 
     def __truediv__(self, other):
-        return self.value / other
+        return self._value / other
 
     def __rtruediv__(self, other):
-        return other / self.value
+        return other / self._value
 
     def __itruediv__(self, other):
-        self.value /= other
+        self._value /= other
         return self
 
     def __floordiv__(self, other):
-        return self.value // other
+        return self._value // other
 
     def __rfloordiv__(self, other):
-        return other // self.value
+        return other // self._value
 
     def __ifloordiv__(self, other):
-        self.value //= other
+        self._value //= other
         return self
 
     def __mod__(self, other):
-        return self.value % other
+        return self._value % other
 
     def __rmod__(self, other):
-        return other % self.value
+        return other % self._value
 
     def __imod__(self, other):
-        self.value %= other
+        self._value %= other
         return self
 
     def __divmod__(self, other):
-        return divmod(self.value, other)
+        return divmod(self._value, other)
 
     def __rdivmod__(self, other):
-        return divmod(other, self.value)
+        return divmod(other, self._value)
 
     def __pow__(self, other):
-        return self.value**other
+        return self._value**other
 
     def __rpow__(self, other):
-        return other**self.value
+        return other**self._value
 
     def __ipow__(self, other):
-        self.value **= other
+        self._value **= other
         return self
 
     def __lshift__(self, other):
-        return self.value << other
+        return self._value << other
 
     def __rlshift__(self, other):
-        return other << self.value
+        return other << self._value
 
     def __ilshift__(self, other):
-        self.value <<= other
+        self._value <<= other
         return self
 
     def __rshift__(self, other):
-        return self.value >> other
+        return self._value >> other
 
     def __rrshift__(self, other):
-        return other >> self.value
+        return other >> self._value
 
     def __irshift__(self, other):
-        self.value >>= other
+        self._value >>= other
         return self
 
     def __and__(self, other):
-        return self.value & other
+        return self._value & other
 
     def __rand__(self, other):
-        return other & self.value
+        return other & self._value
 
     def __iand__(self, other):
-        self.value &= other
+        self._value &= other
         return self
 
     def __xor__(self, other):
-        return self.value ^ other
+        return self._value ^ other
 
     def __rxor__(self, other):
-        return other ^ self.value
+        return other ^ self._value
 
     def __ixor__(self, other):
-        self.value ^= other
+        self._value ^= other
         return self
 
     def __or__(self, other):
-        return self.value | other
+        return self._value | other
 
     def __ror__(self, other):
-        return other | self.value
+        return other | self._value
 
     def __ior__(self, other):
-        self.value |= other
+        self._value |= other
         return self
 
     def __neg__(self):
-        return -self.value
+        return -self._value
 
     def __pos__(self):
-        return +self.value
+        return +self._value
 
     def __abs__(self):
-        return abs(self.value)
+        return abs(self._value)
 
     def __invert__(self):
-        return ~self.value
+        return ~self._value
 
     def __len__(self):
-        return len(self.value)
+        return len(self._value)
 
 
 def get_attribute_or_create(obj, attr, default):

tests/structs/test_bags.py

@@ -5,7 +5,7 @@ from bonobo import Bag
 from bonobo.constants import INHERIT_INPUT
 from bonobo.structs import Token
 
-args = ('foo', 'bar',)
+args = ('foo', 'bar', )
 kwargs = dict(acme='corp')
 
 
@@ -34,29 +34,29 @@ def test_inherit():
     bag3 = bag.extend('c', c=3)
     bag4 = Bag('d', d=4)
 
-    assert bag.args == ('a',)
+    assert bag.args == ('a', )
     assert bag.kwargs == {'a': 1}
     assert bag.flags is ()
 
-    assert bag2.args == ('a', 'b',)
+    assert bag2.args == ('a', 'b', )
     assert bag2.kwargs == {'a': 1, 'b': 2}
     assert INHERIT_INPUT in bag2.flags
 
-    assert bag3.args == ('a', 'c',)
+    assert bag3.args == ('a', 'c', )
     assert bag3.kwargs == {'a': 1, 'c': 3}
     assert bag3.flags is ()
 
-    assert bag4.args == ('d',)
+    assert bag4.args == ('d', )
     assert bag4.kwargs == {'d': 4}
     assert bag4.flags is ()
 
     bag4.set_parent(bag)
-    assert bag4.args == ('a', 'd',)
+    assert bag4.args == ('a', 'd', )
     assert bag4.kwargs == {'a': 1, 'd': 4}
     assert bag4.flags is ()
 
     bag4.set_parent(bag3)
-    assert bag4.args == ('a', 'c', 'd',)
+    assert bag4.args == ('a', 'c', 'd', )
     assert bag4.kwargs == {'a': 1, 'c': 3, 'd': 4}
     assert bag4.flags is ()
 

tests/test_basics.py

@@ -1,7 +1,8 @@
 from unittest.mock import MagicMock
 
-import bonobo
 import pytest
+
+import bonobo
 from bonobo.config.processors import ContextCurrifier
 from bonobo.constants import NOT_MODIFIED
 
@@ -10,14 +11,12 @@ def test_count():
     with pytest.raises(TypeError):
         bonobo.count()
 
+
     context = MagicMock()
 
-    currified = ContextCurrifier(bonobo.count)
-    currified.setup(context)
-
-    for i in range(42):
-        currified()
-    currified.teardown()
+    with ContextCurrifier(bonobo.count).as_contextmanager(context) as stack:
+        for i in range(42):
+            stack()
 
     assert len(context.method_calls) == 1
     bag = context.send.call_args[0][0]
@@ -32,18 +31,31 @@ def test_identity():
 
 
 def test_limit():
-    limit = bonobo.Limit(2)
-    results = []
-    for i in range(42):
-        results += list(limit())
+    context, results = MagicMock(), []
+
+    with ContextCurrifier(bonobo.Limit(2)).as_contextmanager(context) as stack:
+        for i in range(42):
+            results += list(stack())
+
     assert results == [NOT_MODIFIED] * 2
 
 
 def test_limit_not_there():
-    limit = bonobo.Limit(42)
-    results = []
-    for i in range(10):
-        results += list(limit())
+    context, results = MagicMock(), []
+
+    with ContextCurrifier(bonobo.Limit(42)).as_contextmanager(context) as stack:
+        for i in range(10):
+            results += list(stack())
+
+    assert results == [NOT_MODIFIED] * 10
+
+def test_limit_default():
+    context, results = MagicMock(), []
+
+    with ContextCurrifier(bonobo.Limit()).as_contextmanager(context) as stack:
+        for i in range(20):
+            results += list(stack())
+
     assert results == [NOT_MODIFIED] * 10
 
 

tests/util/test_compat.py

@@ -21,4 +21,3 @@ def test_deprecated_alias():
 
     with pytest.warns(DeprecationWarning):
         foo()
-

tests/util/test_objects.py

@@ -35,6 +35,7 @@ def test_wrapper_name():
 
 def test_valueholder():
     x = ValueHolder(42)
+
     assert x == 42
     x += 1
     assert x == 43