Python truncate a long string

Question

How does one truncate a string to 75 characters in Python   This is how it is done in JavaScript   var data  saddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsaddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsadddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd  var info    data length  gt  75    data substring 0 75           data

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You could use this one-liner   data    data  75          if len data   gt  75 else data

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Even shorter    info   data  75     data 75   and

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info   data  min len data   75

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You can t actually  truncate  a Python string like you can do a dynamically allocated C string  Strings in Python are immutable  What you can do is slice a string as described in other answers  yielding a new string containing only the characters defined by the slice offsets and step  In some  non-practical  cases this can be a little annoying  such as when you choose Python as your interview language and the interviewer asks you to remove duplicate characters from a string in-place  Doh

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This method doesn t use any if    data  75    bool data 75

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This just in   n   8 s    123  print  s  n-3     s n-3           len s   gt  n  s    12345678  print  s  n-3     s n-3           len s   gt  n  s    123456789       print  s  n-3     s n-3           len s   gt  n  s    123456789012345  print  s  n-3     s n-3           len s   gt  n   123 12345678 12345    12345

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There s no need for a regular expression but you do want to use string formatting rather than the string concatenation in the accepted answer    This is probably the most canonical  Pythonic way to truncate the string data at 75 characters    gt  gt  gt  data    saddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsaddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsadddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd   gt  gt  gt  info          format data  75   if len data   gt  75 else data  gt  gt  gt  info  111111111122222222223333333333444444444455555555556666666666777777777788888

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gt  gt  gt  info   lambda data  len data  gt 10 and data  10        or data         gt  gt  gt  info  sdfsdfsdfsdfsdfsdfsdfsdfsdfsdfsdf               sdfsdfsdfs             gt  gt  gt  info  sdfsdf               sdfsdf          gt  gt  gt

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Here s a function I made as part of a new String class    It allows adding a suffix   if the string is size after trimming and adding it is long enough - although you don t need to force the absolute size    I was in the process of changing a few things around so there are some useless logic costs   if  truncate     for instance   where it is no longer necessary and there is a return at the top     But  it is still a good function for truncating data           Truncate characters of a string after  len nth char  if necessary    If  len is less than 0  don t truncate anything    Note  If you attach a suffix  and you enable absolute max length then the suffix length is subtracted from max length    Note  If the suffix length is longer than the output then no suffix is used          Usage  Where  text    Testing    width   4          data   String Truncate   text   width                             Test          data   String Truncate   text   width        True                 Te         Equivalent Alternates  Where  text    Testing    width   4          data   String SubStr   text  0   width                            Test          data    text      width                                           Test          data      text        width                                       Test    def Truncate   text   max len   -1   suffix   False   absolute max len   True           Length of the string we are considering for truncation      len              len   text           Whether or not we have to truncate      truncate           False  True     len  gt   max len           Note  If we don t need to truncate  there s no point in proceeding        if   not  truncate            return  text         The suffix in string form      suffix str              str   suffix       truncate and  suffix    False           The suffix length      len suffix       len   suffix str           Whether or not we add the suffix      add suffix         False  True     truncate and  suffix    False and  max len  gt   len suffix           Suffix Offset      suffix offset    max len -  len suffix      suffix offset       max len   suffix offset     add suffix and  absolute max len    False and  suffix offset  gt  0           The truncate point     If not necessary  then length of string   If necessary then the max length with or without subtracting the suffix length    Note  It may be easier   less logic cost   to simply add the suffix to the calculated point  then truncate - if point is negative then the suffix will be destroyed anyway         If we don t need to truncate  then the length is the length of the string   If we do need to truncate  then the length depends on whether we add the suffix and offset the length of the suffix or not         len truncate        len   max len     truncate        len truncate        len truncate   max len     len truncate  lt    max len           If we add the suffix  add it    Suffix won t be added if the suffix is the same length as the text being output        if    add suffix             text    text  0    suffix offset      suffix str    text   suffix offset            Return the text after truncating        return  text     len truncate

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For a Django solution  which has not been mentioned in the question    from django utils text import Truncator value   Truncator value  chars 75    Have a look at Truncator s source code to appreciate the problem  https   github com django django blob master django utils text py L66  Concerning truncation with Django  Django HTML truncation

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info   data  75          if len data   gt  75 else

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info    data  75          if len data   gt  75 else data

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With regex   re sub r     75          g lt 1 gt       data    Long strings are truncated    gt  gt  gt  data  11111111112222222222333333333344444444445555555555666666666677777777778888888888   gt  gt  gt  re sub r     75          g lt 1 gt       data   111111111122222222223333333333444444444455555555556666666666777777777788888       Shorter strings never get truncated    gt  gt  gt  data  11111111112222222222333333   gt  gt  gt  re sub r     75          g lt 1 gt       data   11111111112222222222333333    This way  you can also  cut  the middle part of the string  which is nicer in some cases   re sub r     5       5        g lt 1 gt     g lt 2 gt    data    gt  gt  gt  data  11111111112222222222333333333344444444445555555555666666666677777777778888888888   gt  gt  gt  re sub r     5       5        g lt 1 gt     g lt 2 gt    data   11111   88888

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Even more concise   data   data  75    If it is less than 75 characters there will be no change

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Yet another solution   With True and False you get a little feedback about the test at the end   data    True  data  75          False  data  len data   gt  75

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limit   75 info   data  limit            len data   gt  limit

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If you are using Python 3 4   you can use textwrap shorten from the standard library      Collapse and truncate the given text to fit in the given width       First the whitespace in text is collapsed  all whitespace is replaced   by single spaces   If the result fits in the width  it is returned    Otherwise  enough words are dropped from the end so that the remaining   words plus the placeholder fit within width    gt  gt  gt  textwrap shorten  Hello  world    width 12   Hello world    gt  gt  gt  textwrap shorten  Hello  world    width 11   Hello         gt  gt  gt  textwrap shorten  Hello world   width 10  placeholder         Hello

[python] Python truncate a long string

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