How do I remove a substring from the end of a string in Python

Question

I have the following code   url    abcdc com  print url strip   com      I expected  abcdc  I got  abcd  Now I do   url rsplit   com   1    Is there a better way

User · Answer

Depends on what you know about your url and exactly what you're tryinh to do. If you know that it will always end in '.com' (or '.net' or '.org') then

 url=url[:-4]

is the quickest solution. If it's a more general URLs then you're probably better of looking into the urlparse library that comes with python.

If you on the other hand you simply want to remove everything after the final '.' in a string then

url.rsplit('.',1)[0]

will work. Or if you want just want everything up to the first '.' then try

url.split('.',1)[0]

User · Answer

Python    3 9    abcdc com  removesuffix   com     Python  lt  3 9   def remove suffix text  suffix       if text endswith suffix           text   text  -len suffix       return text  remove suffix  abcdc com     com

User · Answer

You can use split    abccomputer com  split   com  1  0     abccomputer

User · Answer

Here i have a simplest code   url url split      0

User · Answer

DSCLAIMER This method has a critical flaw in that the partition is not anchored to the end of the url and may return spurious results  For example  the result for the URL  quot www comcast net quot  is  quot www quot   incorrect  instead of the expected  quot www comcast net quot   This solution therefore is evil  Don t use it unless you know what you are doing  url rpartition   com   0   This is fairly easy to type and also correctly returns the original string  no error  when the suffix   com  is missing from url

User · Answer

If you mean to only strip the extension       join  abcdc com  split       -1      abcdc    It works with any extension  with potential other dots existing in filename as well  It simply splits the string as a list on dots and joins it without the last element

User · Answer

Starting in Python 3 9  you can use removesuffix instead   abcdc com  removesuffix   com      abcdc

User · Answer

If you know it s an extension  then  url    abcdc com      url rsplit      1  0     split at      starting from the right  maximum 1 split   This works equally well with abcdc com or www abcdc com or abcdc  anything  and is more extensible

User · Answer

Assuming you want to remove the domain  no matter what it is   com   net  etc   I recommend finding the   and removing everything from that point on   url    abcdc com  dot index   url rfind      url   url  dot index    Here I m using rfind to solve the problem of urls like abcdc com net which should be reduced to the name abcdc com    If you re also concerned about www s  you should explicitly check for them   if url startswith  www        url   url replace  www       1    The 1 in replace is for strange edgecases like www net www com  If your url gets any wilder than that look at the regex answers people have responded with

User · Answer

Since it seems like nobody has pointed this on out yet   url    www example com  new url   url  url rfind         This should be more efficient than the methods using split   as no new list object is created  and this solution works for strings with several dots

User · Answer

How about url  -4

User · Answer

If you need to strip some end of a string if it exists otherwise do nothing  My best solutions  You probably will want to use one of first 2 implementations however I have included the 3rd for completeness  For a constant suffix  def remove suffix v  s       return v  -len s   if v endswith s  else v remove suffix  quot abc com quot    quot  com quot       abc  remove suffix  quot abc quot    quot  com quot       abc   For a regex  def remove suffix compile suffix pattern       r   re compile f quot        suffix pattern     quot       return lambda v  r match v  1  remove domain   remove suffix compile r quot    a-zA-Z0-9  3   quot   remove domain  quot abc com quot       quot abc quot  remove domain  quot sub abc net quot       quot sub abc quot  remove domain  quot abc  quot       quot abc  quot  remove domain  quot abc quot       quot abc quot   For a collection of constant suffixes the asymptotically fastest way for a large number of calls  def remove suffix preprocess  suffixes       suffixes   set suffixes      try          suffixes remove         except KeyError          pass      def helper suffixes  pos           if len suffixes     1              suf   suffixes 0              l   -len suf              ls   slice 0  l              return lambda v  v ls  if v endswith suf  else v         si   iter suffixes          ml   len next si           exact   False         for suf in si              l   len suf              if -l    pos                  exact   True             else                  ml   min len suf   ml          ml   -ml         suffix dict              for suf in suffixes              sub   suf ml pos              if sub in suffix dict                  suffix dict sub  append suf              else                  suffix dict sub     suf          if exact              del suffix dict                 for key in suffix dict                  suffix dict key    helper  s  pos  for s in suffix dict key    None              return lambda v  suffix dict get v ml pos   lambda v  v  v  pos           else              for key in suffix dict                  suffix dict key    helper suffix dict key   ml              return lambda v  suffix dict get v ml pos   lambda v  v  v      return helper tuple suffixes   None  domain remove   remove suffix preprocess  quot  com quot    quot  net quot    quot  edu quot    quot  uk quot     tv     co uk     org uk    the final one is probably significantly faster in pypy then cpython  The regex variant is likely faster than this for virtually all cases that do not involve huge dictionaries of potential suffixes that cannot be easily represented as a regex at least in cPython  In PyPy the regex variant is almost certainly slower for large number of calls or long strings even if the re module uses a DFA compiling regex engine as the vast majority of the overhead of the lambda s will be optimized out by the JIT  In cPython however the fact that your running c code for the regex compare almost certainly outweighs the algorithmic advantages of the suffix collection version in almost all cases  Edit  https   m xkcd com 859

User · Answer

In one line   text if not text endswith suffix  or len suffix     0 else text  -len suffix

User · Answer

This is a perfect use for regular expressions    gt  gt  gt  import re  gt  gt  gt  re match r       com    hello com   group 1   hello

User · Answer

If you are sure that the string only appears at the end  then the simplest way would be to use  replace    url    abcdc com  print url replace   com

User · Answer

import re  def rm suffix url    abcdc com   suffix    com        return re sub suffix          url     I want to repeat this answer as the most expressive way to do it  Of course  the following would take less CPU time   def rm dotcom url    abcdc com        return url  -4  if url endswith   com   else url    However  if CPU is the bottle neck why write in Python   When is CPU a bottle neck anyway  In drivers  maybe   The advantages of using regular expression is code reusability  What if you next want to remove   me   which only has three characters   Same code would do the trick    gt  gt  gt  rm sub  abcdc me    me    abcdc

User · Answer

Because this is a very popular question i add another  now available  solution  With python 3 9  https   docs python org 3 9 whatsnew 3 9 html  the function removesuffix   will be added  and removeprefix    and this function is exactly what was questioned here  url    abcdc com  print url removesuffix   com     output   abcdc   PEP 616  https   www python org dev peps pep-0616   shows how it will behave  it is not the real implementation   def removeprefix self  str  prefix  str     - gt  str      if self startswith prefix           return self len prefix        else          return self     and what benefits it has against self-implemented solutions   Less fragile  The code will not depend on the user to count the length of a literal   More performant  The code does not require a call to the Python built-in len function nor to the more expensive str replace   method   More descriptive  The methods give a higher-level API for code readability as opposed to the traditional method of string slicing

User · Answer

def strip end text  suffix       if suffix and text endswith suffix           return text  -len suffix       return text

User · Answer

In my case I needed to raise an exception so I did   class UnableToStripEnd Exception          A Exception type to indicate that the suffix cannot be removed from the text           staticmethod     def get exception text  suffix           return UnableToStripEnd  Could not find suffix   0   on text   1                                     format suffix  text     def strip end text  suffix          Removes the end of a string  Otherwise fails         if not text endswith suffix           raise UnableToStripEnd get exception text  suffix      return text  len text -len suffix

User · Answer

For urls  as it seems to be a part of the topic by the given example   one can do something like this   import os url    http   www stackoverflow com  name ext   os path splitext url  print  name  ext    Or  ext       url split      -1  name   url  -len ext   print  name  ext    Both will output    http   www stackoverflow     com    This can also be combined with str endswith suffix  if you need to just split   com   or anything specific

User · Answer

I used the built-in rstrip function to do it like follow   string    test com  suffix     com  newstring   string rstrip suffix  print newstring  test

User · Answer

strip doesn t mean  quot remove this substring quot   x strip y  treats y as a set of characters and strips any characters in that set from both ends of x  On Python 3 9 and newer you can use the removeprefix and removesuffix methods to remove an entire substring from either side of the string  url    abcdc com  url removesuffix   com        Returns  abcdc  url removeprefix  abcdc       Returns  com   The relevant Python Enhancement Proposal is PEP-616  On Python 3 8 and older you can use endswith and slicing  url    abcdc com  if url endswith   com        url   url  -4   Or a regular expression  import re url    abcdc com  url   re sub    com        url

User · Answer

A broader solution  adding the possibility to replace the suffix  you can remove by replacing with the empty string  and to set the maximum number of replacements  def replacesuffix s old new    limit 1        quot  quot  quot      String suffix replace  if the string ends with the suffix given by parameter  old   such suffix is replaced with the string given by parameter  new   The number of replacements is limited by parameter  limit   unless  limit  is negative  meaning no limit         param s  the input string      param old  the suffix to be replaced      param new  the replacement string  Default value the empty string  suffix is removed without replacement        param limit  the maximum number of replacements allowed  Default value 1       returns  the input string with a certain number  depending on parameter  limit   of the rightmost occurrences of string given by parameter  old  replaced by string given by parameter  new       quot  quot  quot      if s len s -len old       old and limit    0          return replacesuffix s  len s -len old   old new limit-1    new     else          return s  In your case  given the default arguments  the desired result is obtained with  replacesuffix  abcdc com    com    gt  gt  gt   abcdc   Some more general examples  replacesuffix  whatever-qweqweqwe   qwe   N  2   gt  gt  gt   whatever-qweNN   replacesuffix  whatever-qweqweqwe   qwe   N  -1   gt  gt  gt   whatever-NNN   replacesuffix  12 53000   0      -1   gt  gt  gt   12 53

[python] How do I remove a substring from the end of a string in Python?

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