[Numpy-svn] r3949 - in trunk/numpy/lib: . tests

[numpy-svn at scipy.org]

Author: stefan
Date: 2007-08-06 07:42:58 -0500 (Mon, 06 Aug 2007)
New Revision: 3949

Modified:
   trunk/numpy/lib/polynomial.py
   trunk/numpy/lib/tests/test_polynomial.py
Log:
Fix string conversion of polynomial when leading coefficients are
zero. Closes ticket #564.


Modified: trunk/numpy/lib/polynomial.py
===================================================================
--- trunk/numpy/lib/polynomial.py	2007-08-06 09:51:47 UTC (rev 3948)
+++ trunk/numpy/lib/polynomial.py	2007-08-06 12:42:58 UTC (rev 3949)
@@ -500,11 +500,15 @@
         return self.order
 
     def __str__(self):
-        N = self.order
         thestr = "0"
         var = self.variable
-        for k in range(len(self.coeffs)):
-            coefstr ='%.4g' % abs(self.coeffs[k])
+
+        # Remove leading zeros
+        coeffs = self.coeffs[NX.logical_or.accumulate(self.coeffs != 0)]
+        N = len(coeffs)-1
+
+        for k in range(len(coeffs)):
+            coefstr ='%.4g' % abs(coeffs[k])
             if coefstr[-4:] == '0000':
                 coefstr = coefstr[:-5]
             power = (N-k)
@@ -533,11 +537,11 @@
 
             if k > 0:
                 if newstr != '':
-                    if self.coeffs[k] < 0:
+                    if coeffs[k] < 0:
                         thestr = "%s - %s" % (thestr, newstr)
                     else:
                         thestr = "%s + %s" % (thestr, newstr)
-            elif (k == 0) and (newstr != '') and (self.coeffs[k] < 0):
+            elif (k == 0) and (newstr != '') and (coeffs[k] < 0):
                 thestr = "-%s" % (newstr,)
             else:
                 thestr = newstr

Modified: trunk/numpy/lib/tests/test_polynomial.py
===================================================================
--- trunk/numpy/lib/tests/test_polynomial.py	2007-08-06 09:51:47 UTC (rev 3948)
+++ trunk/numpy/lib/tests/test_polynomial.py	2007-08-06 12:42:58 UTC (rev 3949)
@@ -82,5 +82,17 @@
     def check_roots(self):
         assert_array_equal(N.roots([1,0,0]), [0,0])
 
+    def check_str_leading_zeros(self):
+        p = N.poly1d([4,3,2,1])
+        p[3] = 0
+        assert_equal(str(p),
+                     "   2\n"
+                     "3 x + 2 x + 1")
+
+        p = N.poly1d([1,2])
+        p[0] = 0
+        p[1] = 0
+        assert_equal(str(p), " \n0")
+
 if __name__ == "__main__":
     NumpyTest().run()