How many times a substring occurs

Question

How can I count the number of times a given substring is present within a string in Python   For example    gt  gt  gt   foo bar foo  numberOfOccurrences  foo   2

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For a simple string with space delimitation  using Dict would be quite fast  please see the code as below  def getStringCount mnstr str  sbstr str    - gt int          Assumes two inputs string giving the string and          substring to look for number of occurances          Returns the number of occurances of a given string             x   dict       x sbstr    0     sbstr   sbstr strip       for st in mnstr split               if st not in  sbstr               continue         try              x st   1         except KeyError              x st    1     return x sbstr   s    foo bar foo test one two three foo bar  getStringCount s  foo

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def count substring string  sub string       k len string      m len sub string      i 0     l 0     count 0     while l lt k          if string l l m   sub string              count count 1         l l 1     return count  if   name         main         string   input   strip       sub string   input   strip        count   count substring string  sub string      print count

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s   input  enter the main string     p input  enter the substring     l    for i in range len s        l append s i i len p    print l count p

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string  abc  mainstr  ncnabckjdjkabcxcxccccxcxcabc  count 0 for i in range 0 len mainstr        k 0     while k lt len string            if string k   mainstr i k                k  1         else              break        if k  len string            count  1     print count

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You can count the frequency using two ways    Using the count   in str   a count b  Or  you can use   len a split b  -1   Where a is the string and b is the substring whose frequency is to be calculated

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Depending what you really mean  I propose the following solutions    You mean a list of space separated sub-strings and want to know what is the sub-string position number among all sub-strings   s    sub1 sub2 sub3  s split   index  sub2    gt  gt  gt  1  You mean the char-position of the sub-string in the string   s find  sub2    gt  gt  gt  5  You mean the  non-overlapping  counts of appearance of a su-bstring   s count  sub2    gt  gt  gt  1 s count  sub    gt  gt  gt  3

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The question isn t very clear  but I ll answer what you are  on the surface  asking   A string S  which is L characters long  and where S 1  is the first character of the string and S L  is the last character  has the following substrings    The null string     There is one of these   For every value A from 1 to L  for every value B from A to L  the string S A   S B   inclusive   There are L   L-1   L-2       1 of these strings  for a total of 0 5 L  L 1    Note that the second item includes S 1   S L   i e  the entire original string S    So  there are 0 5 L  L 1    1 substrings within a string of length L  Render that expression in Python  and you have the number of substrings present within the string

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counting occurence of a substring in another string  overlapping non overlapping  s   input  enter the main string      e g   bobazcbobobegbobobgbobobhaklpbobawanbobobobob  p input  enter the substring      e g   bob   counter 0 c 0  for i in range len s -len p  1       for j in range len p            if s i j   p j               if c lt len p                   c c 1                 if c  len p                       counter  1                     c 0                     break                 continue         else              break print  number of occurences of the substring in the main string is    counter

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string count substring   like in    gt  gt  gt   abcdabcva  count  ab   2   Update   As pointed up in the comments  this is the way to do it for non overlapping occurrences  If you need to count overlapping occurrences  you d better check the answers at   Python regex find all overlapping matches    or just check my other answer below

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Scenario 1  Occurrence of a word in a sentence  eg  str1    This is an example and is easy   The occurrence of the word  is   lets str2    is   count   str1 count str2    Scenario 2   Occurrence of pattern in a sentence   string    ABCDCDC  substring    CDC   def count substring string sub string       len1   len string      len2   len sub string      j  0     counter   0     while j  lt  len1           if string j     sub string 0                if string j j len2     sub string                   counter    1         j    1      return counter   Thanks

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my string      Strings are amongst the most popular data types in Python                  We can create the strings by enclosing characters in quotes                 Python treats single quotes the same as double quotes      Count   my string lower   strip   n   split      count  string   Count   my string lower   strip   n   split      count  strings   print  The number of occurance of word String is       Count  print  The number of occurance of word Strings is       Count

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If you want to count all the sub-string  including overlapped  then use this method   import re def count substring string  sub string       regex         sub string           print regex      return len re findall regex string

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Here s the solution in Python 3 and case insensitive   s    foo bar foo  upper   sb    foo  upper   results   0 sub len   len sb  for i in range len s        if s i i sub len     sb          results    1 print results

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s    arunununghhjj  sb    nun  results   0 sub len   len sb  for i in range len s        if s i i sub len     sb          results    1 print results

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Below logic will work for all string  amp  special characters  def cnt substr inp str  sub str       inp join str      join inp str split        sub join str      join sub str split         return inp join str count sub join str   print cnt substr  the sky is    blue and not greenthe sky is    blue and not green    the sky

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Risking a downvote because 2  others have already provided this solution  I even upvoted one of them   But mine is probably the easiest for newbies to understand   def count substring string  sub string       slen    len string      sslen   len sub string      range s   slen - sslen   1     count   0     for i in range range s           if  string i i sslen     sub string               count    1     return count

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How about a one-liner with a list comprehension   Technically its 93 characters long  spare me PEP-8 purism   The regex findall answer is the most readable if its a high level piece of code   If you re building something low level and don t want dependencies  this one is pretty lean and mean   I m giving the overlapping answer   Obviously just use count like the highest score answer if there isn t overlap   def count substring string  sub string       return len  i for i in range len string   if string i i len sub string      sub string

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The best way to find overlapping sub-string in a given string is to use the python regular expression it will find all the overlapping matching using the regular expression library  Here is how to do it left is the substring and in right you will provide the string to match  print len re findall     aa    caaaab    3

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import re d    m start   for m in re finditer seaching  string    print  d    This finds the number of times sub string found in the string and displays index

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One way is to use re subn  For example  to count the number of occurrences of  hello  in any mix of cases you can do   import re    count   re subn r hello       astring  flags re I  print  Found   count   occurrences of  hello

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To find overlapping occurences of a substring in a string in Python 3  this algorithm will do   def count substring string sub string       l len sub string      count 0     for i in range len string -len sub string  1           if string i i len sub string      sub string                      count  1     return count     I myself checked this algorithm and it worked

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j   0     while i  lt  len string           sub string out   string i len sub string  j          if sub string    sub string out              count    1         i    1         j    1     return count

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def count substring string  sub string       counterList   1 for i in range len string -len sub string  1  if string i i len sub string      sub string      count sum counterList      return count  if   name         main         string   input   strip       sub string   input   strip        count   count substring string  sub string      print count

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The current best answer involving method count doesn t really count for overlapping occurrences and doesn t care about empty sub-strings as well  For example         gt  gt  gt  a    caatatab   gt  gt  gt  b    ata   gt  gt  gt  print a count b    overlapping 1  gt  gt  gt print a count       empty string 9   The first answer should be 2 not 1  if we consider the overlapping substrings  As for the second answer it s better if an empty sub-string returns 0 as the asnwer   The following code takes care of these things   def num of patterns astr pattern       astr  pattern   astr strip    pattern strip       if pattern        return 0      ind  count  start flag   0 0 0     while True          try              if start flag    0                  ind   astr index pattern                  start flag   1             else                  ind    1   astr ind 1   index pattern              count    1         except              break     return count   Now when we run it    gt  gt  gt num of patterns  caatatab    ata    overlapping 2  gt  gt  gt num of patterns  caatatab        empty string 0  gt  gt  gt num of patterns  abcdabcva   ab    normal 2

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I m not sure if this is something looked at already  but I thought of this as a solution for a word that is  disposable    for i in xrange len word    if word  len term      term      count    1 word   word 1    print count   Where word is the word you are searching in and term is the term you are looking for

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Overlapping occurences   def olpcount string pattern case sensitive True       if case sensitive    True          string    string lower           pattern   pattern lower       l   len pattern      ct   0     for c in range 0 len string            if string c c l     pattern              ct    1     return ct  test    my maaather lies over the oceaaan  print test print olpcount test  a   print olpcount test  aa   print olpcount test  aaa     Results   my maaather lies over the oceaaan 6 4 2

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If you re looking to count the whole string this can works   stri count  If you re looking to count the whole string this can works  print len stri count

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def count substring string  sub string       inc   0     for i in range 0  len string            slice object   slice i len sub string  i          count   len string slice object           if count    len sub string                if sub string    string slice object                    inc   inc   1     return inc  if   name         main         string   input   strip       sub string   input   strip        count   count substring string  sub string      print count

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If you want to find out the count of substring inside any string  please use below code  The code is easy to understand that s why i skipped the comments      string raw input   sub string raw input   start 0 answer 0 length len string  index string find sub string start length  while index lt  gt -1      start index 1     answer answer 1     index string find sub string start length  print answer

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I will keep my accepted answer as the  simple and obvious way to do it  - however  that does not cover overlapping occurrences   Finding out those can be done naively  with multiple checking of the slices - as in      sum  GCAAAAAGH  i   startswith  AAA   for i in range len  GCAAAAAGH       which yields 3  - it can be done by trick use of regular expressions  as can be seen at Python regex find all overlapping matches  - and it can also make for fine code golfing - This is my  hand made  count for overlappingocurrences of patterns in a string which tries not to be extremely naive  at least it does not create new string objects at each interaction    def find matches overlapping text  pattern       lpat   len pattern  - 1     matches          text   array  u   text      pattern   array  u   pattern      indexes          for i in range len text  - lpat           if text i     pattern 0               indexes i    -1         for index  counter in list indexes items                 counter    1             if text i     pattern counter                   if counter    lpat                      matches append index                      del indexes index                  else                      indexes index    counter             else                  del indexes index      return matches  def count matches text  pattern       return len find matches overlapping text  pattern

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If you re looking for a power solution that works every case this function should work   def count substring string  sub string       ans   0     for i in range len string - len sub string -1            if sub string    string i len sub string  i               ans    1     return ans

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Here s a solution that works for both non-overlapping and overlapping occurrences  To clarify  an overlapping substring is one whose last character is identical to its first character   def substr count st  sub         If a non-overlapping substring then just       use the standard string  count  method       to count the substring occurences     if sub 0     sub -1           return st count sub         Otherwise  create a copy of the source string        and starting from the index of the first occurence       of the substring  adjust the source string to start       from subsequent occurences of the substring and keep       keep count of these occurences      st   st         start    st index sub      cnt   0      while start is not None          cnt    1         try               st    st start   len sub  - 1               start    st index sub          except  ValueError  IndexError               return cnt      return cnt

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This makes a list of all the occurrences  also overlapping  in the string and counts them   def num occ str1  str2       l1  l2   len str1   len str2      return len  str1 i i   l2  for i in range l1 - l2   1  if str1 i i   l2     str2     Example   str1   abcabcd  str2    bc    will create this list but save only the BOLD values     ab  bc  ca  ab  bc  cd   that will return   len  bc  bc

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For overlapping count we can use use   def count substring string  sub string       count 0     beg 0     while string find sub string beg   -1            count count 1         beg string find sub string beg          beg beg 1     return count   For non-overlapping case we can use count   function   string count sub string

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You could use the startswith method   def count substring string  sub string       x   0     for i in range len string            if string i   startswith sub string               x    1     return x

[python] How many times a substring occurs

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