Hi all, I've been trying to make a class with which to manipulate sound
data, and have run into some behaviour I don't understand which I hope
somebody here can explain. The class has an attribute called data, which
is a list with two elements, one for each audio channel, each of which
is a list containing the audio data for that channel. It also has
various methods to write data such as sine waves and so on, and a method
to insert data from one sound at the start of data from another.
Schematically, the relevant bits look like this:
class sound:
def f(self):
self.data = [[0]]*2
def insert(self, other):
for c in xrange(2):
self.data[c][0:0] = other.data[c]
However, the insert method doesn't work properly; x.insert(y) adds two
copies of y's data to the start of x's data, instead of one. From a
session in IDLE:
>>> x = sound()
>>> y = sound()
>>> x.f()
>>> y.f()
>>> x.data
[[0], [0]]
>>> x.insert(y)
>>> x.data
[[0, 0, 0], [0, 0, 0]]
But suppose I replace the line
self.data = [[0]]*2
with
self.data = [[0] for c in xrange(2)]
Then it works fine:
>>> x = sound()
>>> y = sound()
>>> x.f()
>>> y.f()
>>> x.data
[[0], [0]]
>>> x.insert(y)
>>> x.data
[[0, 0], [0, 0]]
Can anybody tell me what's going on?
--
http://mail.python.org/mailman/listinfo/python-list
