Python: Character/String Manipulation

[last updated: 2026-01-10]
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• There is no separate data type for characters. A single character is simply a string data type with a length of 1.

• Concatenation:
  str1 = "this is a"
  str2 = " test"
  str3 = str1 + str2
  print (str3)
  returns: this is a test

• Get a substring:
  string[start: end: step]
  if step omitted, it defaults to 1
  'start' is the index position of the first character to be included,
  'end' is the index position of the character that is one past the last char to be included
  • negative index numbers:
    Negative index numbers start counting from the end of the string.
    This is confusing, because:
        if counting from the beginning of the string, the first char is index 0
        but if counting from the end of the string, the first char is index -1
    index -2 refers to the next-to-the-last char of the string, etc.
  • str01 = "abcdefg"
    str01[1:] returns 'bcdefg' (no end position defaults to the end of the string
    str01[-3:] returns 'efg', starting with index -3, which starts counting with a -1 at the end of the string
    str02[1:-3] returns 'bcd', end position specified as last char to be included+1, starting counting with -1 at last character of the string
• str1[::2] - returns every other character

• Get a substring using split - actually produces a list of substrings of the original string:
  a_string = "apple,banana,orange"
  fruits = a_string.split(',') # ie. splits based on a 'comma' delimiter
  print(fruits) # Output - a list of strings: ['apple', 'banana', 'orange']

• Regular Expressions (re module) has powerful tools for extracting substrings based on complex delimiter patterns

• Remove characters from the beginning or the end of a string:
  • Remove last char of string - Easiest IMO:
    string[:-1], ie. returns a string composed starting with the first char of the string, and ending one char before the -1 index char, which, being the last char of the string,
    the last char to be returned will be one less than that, or the next-to-the-last char of the string,
    ie, having removed the last char of the string.
  • strip() method:
    eg.: [some string].strip()[-3:]
    gets the last 3 characters of the string.
    (note that...) [some string][-3:] does the same
    however if there is whitespace at the end of the string, the strip() will remove them
    Complication:
    Basically, this will remove any chars inside the () from the end of the string, with an empty() interpreted as command to remove whitespace.
    However if a char to be removed is specified, eg: str01.strip("g")
    then All "g"s at the end of the string will be removed, up to the first non-g character

    --------

  • [string1].find([string2] will return -1 if string 2 is not found in string1
    If it is there, the position of the first character (zero-indexed) will be returned.
    eg. string1 = "this string", string2 = "is", string1.find(string2) will return 2
  • Slicing: [this is ambiguous, because while it's called "slicing", it does not use the .slice command...]
    for string1 = "say what now"
    it includes the first index, but excludes the last
    string1[:2] returns "sa" (the 0 index start position is assumed)
    string1[7:] returns "t now" (the end char is assumed to be the last char of the string)
    string1[-3:] returns "now"

  • Get number of words in a string:
    a_string = "one two three"
    word_list = a_string. split() Split `a_string` by whitespace.
    number_of_words = len(word_list)
    print(number_of_words)

  • Get number of characters in a string:
    a_string = "someText"
    number_of_chars = len(a_string)
    print(number_of_chars)
    the "someText" string will return a length of 8

  • Get Nth word in String:
    # initializing string
    test_str = "GFG is for Geeks"

    # printing original string
    print("The original string is : " + test_str)

    # initializing N
    N = 3

    # Get Nth word in String
    # using loop
    count = 0
    res = ""
    for ele in test_str:
    if ele == ' ':
    count = count + 1
    if count == N:
    break
    res = ""
    else :
    res = res + ele

    # printing result
    print("The Nth word in String : " + res)
    Output :

    The original string is : GFG is for Geeks
    The Nth word in String : for

  • Convert String to list of words:
    • this worked...
      wordList = inStr.split()
      wordList = inStr.split(" ") - this seemed to do the same ...
    • from stackExchange, I think, but didn't work...
      import re
      mystr = 'This is a string, with words!'
      wordList = re.sub("[^\w]", " ", mystr).split()

  • Remove a specific word from a string:
    s = s.replace('papa', '')
  • Remove nth word from string:
    • nreplace=1
      my_string="hello my friend"
      words=my_string.split(" ")
      words[nreplace]="your"
      " ".join(words)
    • OR -
      You can replace the 4th list item using
      my_list[3] = "new"
      And then put it back together with
      my_new_string = " ".join(my_list)
    • del inStr[2]
      will delete the 2nd index element
      del inStr[2:4]
      will delete 2nd & 3rd index element

  • Join elements of a list into a single string:
    wordList = ['this', 'is', 'a', 'sentence']
    newStr = ' '.join(wordList)

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