Iterating each character in a string using Python

Question

In C    I can iterate over an std  string like this   std  string str    Hello World     for  int i   0  i  lt  str length      i        std  cout  lt  lt  str i   lt  lt  std  endl      How do I iterate over a string in Python

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Several answers here use range    xrange is generally better as it returns a generator  rather than a fully-instantiated list   Where memory and or iterables of widely-varying lengths can be an issue  xrange is superior

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Well you can also do something interesting like this and do your job by using for loop   suppose you have variable name name    Mr Suryaa  for index in range   len   name          print   name index     just like c and c      Answer is  M r   S u r y a a  However since range   create a list of the values which is sequence thus you can directly use the name  for e in name      print e    This also produces the same result and also looks better and works with any sequence like list  tuple  and dictionary   We have used tow Built in Functions   BIFs in Python Community     1  range   - range   BIF is used to create indexes     Example  for i in range   5     can produce 0   1   2   3   4   2  len   - len   BIF is used to find out the length of given string

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If you would like to use a more functional approach to iterating over a string  perhaps to transform it somehow   you can split the string into characters  apply a function to each one  then join the resulting list of characters back into a string   A string is inherently a list of characters  hence  map  will iterate over the string - as second argument - applying the function - the first argument - to each one   For example  here I use a simple lambda approach since all I want to do is a trivial modification to the character  here  to increment each character value    gt  gt  gt     join map lambda x  chr ord x  1    HAL     IBM    or more generally    gt  gt  gt     join map my function  my string     where my function takes a char value and returns a char value

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Just to make a more comprehensive answer  the C way of iterating over a string can apply in Python  if you really wanna force a square peg into a round hole   i   0 while i  lt  len str       print str i      i    1   But then again  why do that when strings are inherently iterable   for i in str      print i

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If you need access to the index as you iterate through the string  use enumerate      gt  gt  gt  for i  c in enumerate  test            print i  c      0 t 1 e 2 s 3 t

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Even easier   for c in  test       print c

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As Johannes pointed out    for c in  string        do something with c   You can iterate pretty much anything in python using the for loop construct    for example  open  file txt   returns a file object  and opens the file   iterating over it iterates over lines in that file  with open filename  as f      for line in f            do something with line   If that seems like magic  well it kinda is  but the idea behind it is really simple     There s a simple iterator protocol that can be applied to any kind of object to make the for loop work on it   Simply implement an iterator that defines a next   method  and implement an   iter   method on a class to make it iterable   the   iter   of course  should return an iterator object  that is  an object that defines next     See official documentation

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You can also do the following  txt    quot Hello World  quot  print   txt  sep   n    This does not use loops but internally print statement takes care of it    unpacks the string into a list and sends it to the print statement sep   n  will ensure that the next char is printed on a new line The output will be  H e l l o   W o r l d    If you do need a loop statement  then as others have mentioned  you can use a for loop like this  for x in txt  print  x

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If you ever run in a situation where you need to get the next char of the word using   next      remember to create a string iterator and iterate over it and not the original string  it does not have the   next     method   In this example  when I find a char     I keep looking into the next word while I don t find    so I need to use   next    here a for loop over the string wouldn t help  myString     string  4    RP0    LC0      3  4     3   4     processedInput      word iterator   myString   iter     for idx  char in enumerate word iterator       if char                 continue      processedInput  char      if char                 next char word iterator   next             while next char                    processedInput  next char           next char word iterator   next             else            processedInput  next char

[python] Iterating each character in a string using Python

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