Lecture Notes on 25 Oct 2013

Substrings

You can slice a string into substrings. Consider
the string

st = 'Life of Brian'

The generic way of getting the substring from the 
above string would be to get a slice like so:

st [startIndex : endIndex]

The substring will start at the startIndex but will
end at endIndex - 1. One way of remembering this is
(endIndex - startIndex) is the length of the substring.

Here are four variations of getting the substring

s = st[5:7]       # s = 'of'
s = st[:4]        # s = 'Life'
s = st[8:]        # s = 'Brian'
s = st[:]         # s = 'Life of Brian'

If the startIndex is missing, then it implies the substring 
will start at the beginning of the string. If the endIndex
is missing, then it implies the substring will go all the
way to the end of the string. If both the startIndex and the
endIndex are missing, then you get a copy of the string.


# Code to generate all substrings of a given string
def main():
  st = input ('Enter a string: ')
  len_str = len(st)
  window = len_str
  while (window > 0):
    startIndex = 0
    while (startIndex + window <= len_str):
      print (st[startIndex : startIndex + window])
      startIndex += 1
    window = window - 1

main()