diff -r 1b70e84ac93b pypy/module/micronumpy/interp_numarray.py
--- a/pypy/module/micronumpy/interp_numarray.py Thu Sep 01 15:31:22 2011 +0200
+++ b/pypy/module/micronumpy/interp_numarray.py Thu Sep 01 10:38:52 2011 -0600
@@ -1,11 +1,12 @@
 from pypy.interpreter.baseobjspace import Wrappable
 from pypy.interpreter.error import OperationError
-from pypy.interpreter.gateway import interp2app, unwrap_spec
+from pypy.interpreter.gateway import interp2app, unwrap_spec, NoneNotWrapped
 from pypy.interpreter.typedef import TypeDef, GetSetProperty
 from pypy.module.micronumpy import interp_ufuncs, interp_dtype, signature
 from pypy.rlib import jit
 from pypy.rpython.lltypesystem import lltype
 from pypy.tool.sourcetools import func_with_new_name
+from math import ceil


 numpy_driver = jit.JitDriver(greens = ['signature'],
@@ -561,6 +562,24 @@
         arr.dtype.setitem(arr.storage, i, one)
     return space.wrap(arr)

+@unwrap_spec(start=int, step=int)
+def arange(space, start, w_end=NoneNotWrapped, step=1, w_dtype=None):
+    dtype = space.interp_w(interp_dtype.W_Dtype,
+        space.call_function(space.gettypefor(interp_dtype.W_Dtype), w_dtype)
+    )
+    if w_end is None:
+        start, end = 0, start
+    else:
+        end = space.getindex_w(w_end, None)
+
+    # better way?
+    size = max(int(ceil((end - start) / float(step))), 0)
+
+    arr = SingleDimArray(size, dtype=dtype)
+    for i, val in enumerate(xrange(start, end, step)):
+        arr.dtype.setitem(arr.storage, i, dtype.adapt_val(val))
+    return space.wrap(arr)
+
 BaseArray.typedef = TypeDef(
     'numarray',
     __new__ = interp2app(BaseArray.descr__new__.im_func),