starting to write docs, taking decisions on public api

bonobo/io/file.py

@@ -0,0 +1,35 @@
+from bonobo.util.lifecycle import with_context
+
+__all__ = ['FileWriter', ]
+
+
+@with_context
+class FileWriter:
+    # XXX TODO implement @with_context like this ? Pros and cons ?
+    class Meta:
+        contextual = True
+
+    def __init__(self, path_or_buf, eol='\n'):
+        self.path_or_buf = path_or_buf
+        self.eol = eol
+
+    def initialize(self, ctx):
+        """ todo add lock file ? optional maybe ? """
+        assert not hasattr(ctx, 'fp'), 'One at a time, baby.'
+        ctx.fp = open(self.path_or_buf, 'w+')
+        ctx.first = True
+
+    def write(self, fp, line, prefix=''):
+        fp.write(prefix + line)
+
+    def __call__(self, ctx, row):
+        if ctx.first:
+            prefix, ctx.first = '', False
+        else:
+            prefix = self.eol
+
+        self.write(ctx.fp, row, prefix=prefix)
+
+    def finalize(self, ctx):
+        ctx.fp.close()
+        del ctx.fp, ctx.first