How to get the position of a character in Python

Question

How can I get the position of a character inside a string in python

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gt  gt  gt  s  mystring   gt  gt  gt  s index  r   4  gt  gt  gt  s find  r   4    Long winded  way   gt  gt  gt  for i c in enumerate s         if  r   c  print i     4   to get substring     gt  gt  gt  s  mystring   gt  gt  gt  s 4 10   ring

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Just for completion  in the case I want to find the extension in a file name in order to check it  I need to find the last      in this case use rfind   path    toto titi tata  xls  path find      4 path rfind      15   in my case  I use the following  which works whatever the complete file name is   filename without extension   complete name  complete name rfind

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What happens when the string contains a duplicate character  from my experience with index   I saw that for duplicate you get back the same index   For example   s    abccde  for c in s      print   s   d     c  s index c      would return   a  0 b  1 c  2 c  2 d  4   In that case you can do something like that   for i  character in enumerate my string        i is the position of the character in the string

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more itertools locate is a third-party tool that finds all indicies of items that satisfy a condition   Here we find all index locations of the letter  i    import more itertools as mit   s    supercalifragilisticexpialidocious  list mit locate s  lambda x  x     i       8  13  15  18  23  26  30

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There are two string methods for this  find   and index     The difference between the two is what happens when the search string isn t found   find   returns -1  and index   raises ValueError   Using find     gt  gt  gt  myString    Position of a character   gt  gt  gt  myString find  s   2  gt  gt  gt  myString find  x   -1     Using index     gt  gt  gt  myString    Position of a character   gt  gt  gt  myString index  s   2  gt  gt  gt  myString index  x   Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt  ValueError  substring not found     From the Python manual     string find s  sub   start   end      Return the lowest index in s where the substring sub is found such that sub is wholly contained in s start end   Return -1 on failure  Defaults for start and end and interpretation of negative values is the same as for slices    And      string index s  sub   start   end      Like find   but raise ValueError when the substring is not found

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A solution with numpy for quick access to all indexes   string array   np array list my string   char indexes   np where string array     C

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string find character    string index character      Perhaps you d like to have a look at the documentation to find out what the difference between the two is

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If you want to find the first match  Python has a in-built string method that does the work  index    string index value  start  end   Where   Value      Required  The value to search for  start      Optional  Where to start the search  Default is 0  end        Optional  Where to end the search  Default is to the end of the string   def character index        string    quot Hello World  This is an example sentence with no meaning  quot      match    quot i quot      return string index match           print character index     gt  15  If you want to find all the matches  Let s say you need all the indexes where the character match is and not just the first one  The pythonic way would be to use enumerate    def character indexes        string    quot Hello World  This is an example sentence with no meaning  quot      match    quot i quot       indexes of match           for index  character in enumerate string           if character    match              indexes of match append index      return indexes of match  print character indexes       15  18  42  53   Or even better with a list comprehension  def character indexes comprehension        string    quot Hello World  This is an example sentence with no meaning  quot      match    quot i quot       return  index for index  character in enumerate string  if character    match    print character indexes comprehension       15  18  42  53

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A character might appear multiple times in a string  For example in a string sentence  position of e is 1  4  7  because indexing usually starts from zero   but what I find is both of the functions find   and index   returns first position of a character  So  this can be solved doing this    def charposition string  char       pos       list to store positions for each  char  in  string      for n in range len string            if string n     char              pos append n      return pos  s    sentence  print charposition s   e       Output   1  4  7

User · Answer

Just for a sake of completeness  if you need to find all positions of a character in a string  you can do the following  s    shak spea e  c       print  pos for pos  char in enumerate s  if char    c    which will print   4  9

[python] How to get the position of a character in Python?

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