Speed of string += string

Ben Hutchings do-not-spam-ben.hutchings at businesswebsoftware.com
Tue Apr 15 12:03:31 CEST 2003


In article <mailman.1050173000.12088.python-list at python.org>,
Alan McIntyre wrote:
> Just off the cuff here, it seems to me that the time required to do 
> "string += string" is going to be proportional to the size of the 
> original string whether you do it in Python or with the STL's 
> std::string or with C strings (so long as you don't know beforehand how 
> long the final string will be).
<snip>

Mutable string implementations may allocate more memory than their
current contents require, in order to avoid future reallocation and
copying.  A string implementation that grows its buffer exponentially
(e.g. doubling it every time it needs to grow) will have amortised
linear time complexity for additions, just like the STL vector or
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