Python string class like StringBuilder in C

Question

Is there some string class in Python like StringBuilder in C

User · Answer

Python has several things that fulfill similar purposes     One common way to build large strings from pieces is to grow a list of strings and join it when you are done  This is a frequently-used Python idiom    To build strings incorporating data with formatting  you would do the formatting separately    For insertion and deletion at a character level  you would keep a list of length-one strings   To make this from a string  you d call list your string   You could also use a UserString MutableString for this   c StringIO StringIO is useful for things that would otherwise take a file  but less so for general string building

User · Answer

There is no explicit analogue - i think you are expected to use string concatenations likely optimized as said before  or third-party class i doubt that they are a lot more efficient - lists in python are dynamic-typed so no fast-working char   for buffer as i assume    Stringbuilder-like classes are not premature optimization because of innate feature of strings in many languages immutability  - that allows many optimizations for example  referencing same buffer for slices substrings    Stringbuilder stringbuffer stringstream-like classes work a lot faster than concatenating strings producing many small temporary objects that still need allocations and garbage collection  and even string formatting printf-like tools  not needing of interpreting formatting pattern overhead that is pretty consuming for a lot of format calls

User · Answer

Relying on compiler optimizations is fragile  The benchmarks linked in the accepted answer and numbers given by Antoine-tran are not to be trusted  Andrew Hare makes the mistake of including a call to repr in his methods  That slows all the methods equally but obscures the real penalty in constructing the string   Use join  It s very fast and more robust     ipython3 Python 3 5 1  default  Mar  2 2016  03 38 02   IPython 4 1 2 -- An enhanced Interactive Python   In  1   values    str num  for num in range int 1e3     In  2     timeit            join values           100000 loops  best of 3  7 37   s per loop  In  3     timeit         result              for value in values              result    value          10000 loops  best of 3  82 8   s per loop  In  4   import io  In  5     timeit         writer   io StringIO           for value in values              writer write value          writer getvalue            10000 loops  best of 3  81 8   s per loop

User · Answer

There is no one-to-one correlation   For a really good article please see Efficient String Concatenation in Python      Building long strings in the Python   progamming language can sometimes   result in very slow running code  In   this article I investigate the   computational performance of various   string concatenation methods

User · Answer

Using method 5 from above  The Pseudo File  we can get very good perf and flexibility  from cStringIO import StringIO  class StringBuilder        file str   None       def   init   self            self  file str   StringIO         def Append self  str            self  file str write str        def   str   self            return self  file str getvalue     now using it   sb   StringBuilder    sb Append  Hello n   sb Append  World    print sb

User · Answer

In case you are here looking for a fast string concatenation method in Python  then you do not need a special StringBuilder class  Simple concatenation works just as well without the performance penalty seen in C    resultString       resultString     Append 1  resultString     Append 2    See Antoine-tran s answer for performance results

User · Answer

you can try StringIO or cStringIO

User · Answer

I have used the code of Oliver Crow  link given by Andrew Hare  and adapted it a bit to tailor Python 2 7 3   by using timeit package   I ran on my personal computer  Lenovo T61  6GB RAM  Debian GNU Linux 6 0 6  squeeze     Here is the result for 10 000 iterations    method1   0 0538418292999 secs process size 4800 kb method2   0 22602891922 secs process size 4960 kb method3   0 0605459213257 secs process size 4980 kb method4   0 0544030666351 secs process size 5536 kb method5   0 0551080703735 secs process size 5272 kb method6   0 0542731285095 secs process size 5512 kb   and for 5 000 000 iterations  method 2 was ignored because it ran tooo slowly  like forever     method1   5 88603997231 secs process size 37976 kb method3   8 40748500824 secs process size 38024 kb method4   7 96380496025 secs process size 321968 kb method5   8 03666186333 secs process size 71720 kb method6   6 68192911148 secs process size 38240 kb   It is quite obvious that Python guys have done pretty great job to optimize string concatenation  and as Hoare said   premature optimization is the root of all evil   -

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