[Tutor] saveLine

[Peter Otten]

Avi Gross wrote:

> Alan and others have answered the questions posed and what I am asking now
> is to look at the function he proposed to keep track of the last five
> lines.
> 
> There is nothing wrong with it but I wonder what alternatives people would
> prefer. His code is made for exactly 5 lines to be buffered and is quite
> efficient. But what if you wanted N lines buffered, perhaps showing a
> smaller number of lines on some warnings or errors and the full N in other
> cases?

The standard library features collections.deque. With that:

buffer = collections.deque(maxlen=N)
save_line = buffer.append

This will start with an empty buffer. To preload the buffer:

buffer = collections.deque(itertools.repeat("", N), maxlen=N)

To print the buffer:

print_buffer = sys.stdout.writelines

or, more general:

def print_buffer(items, end=""):
    for item in items:
        print(item, end=end)

Also, for smallish N:

def print_buffer(items, end=""):
    print(*items, sep=end)