Sayan Chatterjee wrote: > Hi Walter, > Thanks a lot! > > Yes, now I get your point. append is working perfectly fine. > > Hi Peter: > > Exactly. It's very nice. Indices needn't have to be mentioned explicitly. > No explicit looping and the thing is done! > > But I have a question, whenever we want to do operations on the individual > array elements, don't we have to mention the indices explicitly i.e > p_za[i]?
For Python's built-in list, yes, but not for numpy arrays. > 1) Traceback (most recent call last): > File "ZA.py", line 44, in <module> > p_za = p_za % 4 > TypeError: unsupported operand type(s) for %: 'list' and 'int' >>> items = [3, 4, 5] >>> items % 2 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unsupported operand type(s) for %: 'list' and 'int' >>> items = numpy.array(items) >>> items % 2 array([1, 0, 1]) Even for lists you can do better than using an explicit index, you can iterate over its members: >>> items = [3, 4, 5] >>> [v % 2 for v in items] [1, 0, 1] > 2) Traceback (most recent call last): > File "ZA.py", line 43, in <module> > if p_za[i] > 4.0: > ValueError: The truth value of an array with more than one element is > ambiguous. Use a.any() or a.all() > > When the i indices are removed * (1) * error message is showing up and > when i is included *(2) *is shown.* * You are probably seeing that error because p_za[i] is a numpy.array, i. e. you have a list of arrays: >>> items = [numpy.array([1,2]), numpy.array([3,4])] >>> items[0] > 4 array([False, False], dtype=bool) >>> if items[0] > 4: pass ... Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() How you managed to get there and what you actually want to achieve -- I can't tell from what you provide. Perhaps you can give a little more context, in code, but more importantly in prose. _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
