How to find char in string and get all the indexes

Question

I got some simple code   def find str  ch       for ltr in str          if ltr    ch              return str index ltr  find  ooottat    o     The function only return the first index  If I change return to print  it will print 0 0 0  Why is this and is there any way to get 0 1 2

User · Answer

This is because str index ch  will return the index where ch occurs the first time  Try   def find s  ch       return  i for i  ltr in enumerate s  if ltr    ch    This will return a list of all indexes you need   P S  Hugh s answer shows a generator function  it makes a difference if the list of indexes can get large   This function can also be adjusted by changing    to

User · Answer

You could try this  def find ch string1       for i in range len string1            if ch    string1 i               pos append i

User · Answer

As the rule of thumb  NumPy arrays often outperform other solutions while working with POD  Plain Old Data  A string is an example of POD and a character too  To find all the indices of only one char in a string  NumPy ndarrays may be the fastest way   def find1 str  ch       0 100 seconds for 1MB str    npbuf   np frombuffer str  dtype np uint8    Reinterpret str as a char buffer   return np where npbuf    ord ch              Find indices with numpy  def find2 str  ch       0 920 seconds for 1MB str    return  i for i  c in enumerate str  if c    ch    Find indices with python

User · Answer

def find idx str  ch       yield  i for i  c in enumerate str  if c    ch   for idx in find idx  babak karchini is a beginner in python     i        print idx   output   11  13  15  23  29

User · Answer

This is slightly modified version of Mark Ransom s answer that works if ch could be more than one character in length   def find term  ch          Find all places with ch in str             for i in range len term            if term i i   len ch      ch              yield i

User · Answer

I would go with Lev  but it s worth pointing out that if you end up with more complex searches that using re finditer may be worth bearing in mind  but re s often cause more trouble than worth - but sometimes handy to know   test    ooottat     i start    i end    for i in re finditer  o   test       0  1    1  2    2  3       i start    i end    for i in re finditer  o    test       0  3

User · Answer

x    abcdabcdabcd  print x  l   -1 while True      l   x find  a   l 1      if l    -1          break     print l

User · Answer

Lev s answer is the one I d use  however here s something based on your original code   def find str  ch       for i  ltr in enumerate str           if ltr    ch              yield i   gt  gt  gt  list find  ooottat    o     0  1  2

User · Answer

All the other answers have two main flaws   They do a Python loop through the string  which is horrifically slow  or They use numpy which is a pretty big additional dependency   def findall haystack  needle       idx   -1     while True          idx   haystack find needle  idx 1          if idx    -1              break         yield idx  This iterates through haystack looking for needle  always starting at where the previous iteration ended  It uses the builtin str find which is much faster than iterating through haystack character-by-character  It doesn t require any new imports

User · Answer

def find offsets haystack  needle               Find the start of all  possibly-overlapping  instances of needle in haystack             offs   -1     while True          offs   haystack find needle  offs 1          if offs    -1              break         else              yield offs  for offs in find offsets  ooottat    o        print offs   results in  0 1 2

[python] How to find char in string and get all the indexes?

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