On Mon, Jul 21, 2008 at 10:31 PM, youtoo <[EMAIL PROTECTED]> wrote: > It has been extensively discussed the time complexity (quadratic) of > string concatenation (due to string's immutability).
Actually, it is roughly linear, at least for reasonable string lengths: $ python -V Python 2.5.2 $ python -mtimeit -s "n=1000; a='#'*n" "a+a" 1000000 loops, best of 3: 1 usec per loop $ python -mtimeit -s "n=10000; a='#'*n" "a+a" 100000 loops, best of 3: 5.88 usec per loop $ python -mtimeit -s "n=100000; a='#'*n" "a+a" 10000 loops, best of 3: 59.8 usec per loop Repeatedly constructing a string by appending a constant number of characters at a time, however, is quadratic in the final string length (although VM optimizations may affect this). > But what is: > > == the time complexity of string indexing? Is it constant? Yes. > == the time complexity of string slicing? Is it O(K) with K the > slice's length? I suspect so, since the time is dominated by the time taken to copy the data into a new string object. > How are strings stored in Python? As arrays? As linked lists? Arrays; see Include/stringobject.h in the Python source distribution. -- David -- http://mail.python.org/mailman/listinfo/python-list
