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Hi bumsfeld,
I believe that the array data structure in the Numeric/NumPy package is both typed and non-resizable, just like C arrays [actually, I'm pretty sure that these data structures are C arrays wearing a Python hat]. Check out:
//numeric.scipy.org
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Thanks G-Do for your information, so NumPy eventually replaces Numeric and Numarray. Interesting!
When I was coding in C, I used to sample lab data and put it into a circular or ring buffer to keep the thing from overflowing. This was an easy way to calculate a moving …
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G-Do 19 Junior Poster
Hi bumsfeld,
I believe that the array data structure in the Numeric/NumPy package is both typed and non-resizable, just like C arrays [actually, I'm pretty sure that these data structures are C arrays wearing a Python hat]. Check out:
//numeric.scipy.org
vegaseat 1,735 DaniWeb's Hypocrite Team Colleague
16 Years AgoThanks G-Do for your information, so NumPy eventually replaces Numeric and Numarray. Interesting!
When I was coding in C, I used to sample lab data and put it into a circular or ring buffer to keep the thing from overflowing. This was an easy way to calculate a moving average.
You can do a similar thing in Python using a list and keeping track of the index. When the index reaches the limit you have set, new data starts at index zero again.
A queue makes this simpler, particularly the deque container, because you can add to the end and pop the front. Here is an example, I hope you can see what is happening:
# the equivalent of a circular size limited list
# also known as ring buffer, pops the oldest data item
# to make room for newest data item when max size is reached
# uses the double ended queue available in Python24
from collections import deque
class RingBuffer[deque]:
"""
inherits deque, pops the oldest data to make room
for the newest data when size is reached
"""
def __init__[self, size]:
deque.__init__[self]
self.size = size
def full_append[self, item]:
deque.append[self, item]
# full, pop the oldest item, left most item
self.popleft[]
def append[self, item]:
deque.append[self, item]
# max size reached, append becomes full_append
if len[self] == self.size:
self.append = self.full_append
def get[self]:
"""returns a list of size items [newest items]"""
return list[self]
# testing
if __name__ == '__main__':
size = 5
ring = RingBuffer[size]
for x in range[9]:
ring.append[x]
print ring.get[] # test
"""
notice that the left most item is popped to make room
result =
[0]
[0, 1]
[0, 1, 2]
[0, 1, 2, 3]
[0, 1, 2, 3, 4]
[1, 2, 3, 4, 5]
[2, 3, 4, 5, 6]
[3, 4, 5, 6, 7]
[4, 5, 6, 7, 8]
"""
bumsfeld 413 Nearly a Posting Virtuoso
16 Years AgoSo the trick is to make size of ring buffer large enough to retain all pertinent data long enough?
I guess the answer is yes.
14 Years Ago
Why not something like:
if len[mylist] > 5:
...del mylist[0]
vegaseat 1,735 DaniWeb's Hypocrite Team Colleague
14 Years AgoWhy not something like:
if len[mylist] > 5:
...del mylist[0]
Good idea, but if mylist is appended to in several different places in your code than it would not be very practical.
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