How efficient is Python substring extraction?

Question

I've got the entire contents of a text file (at least a few KB) in string myStr.

Will the following code create a copy of the string (less the first character) in memory?

myStr = myStr[1:]

I'm hoping it just refers to a different location in the same internal buffer. If not, is there a more efficient way to do this?

Thanks!

Note: I'm using Python 2.5.

Answer 1

At least in 2.6, slices of strings are always new allocations; string_slice() calls PyString_FromStringAndSize(). It doesn't reuse memory--which is a little odd, since with invariant strings, it should be a relatively easy thing to do.

Short of the buffer API (which you probably don't want), there isn't a more efficient way to do this operation.