#this program illustrates many of the basic features of 
#strings in Python.
def stringstuff():
#you can define constant strings
#using either single, double, or triple
#quotes (useful if you include line breaks
#in strings), and assign them to variables.
  s="hello"
  t='goodbye'
  u="""See you
      later"""
  print s
  print t
  print u
#You can also use special sequences to
#indicate nonprinting characters like
#tabs and newlines
  v="\nso much depends\nupon\n\na red wheel\nbarrow\n\nglazed with rain\nwater\n\nbeside the white\nchickens\n\n"
  print v
#You can concatenate strings with +
  print s+"\t"+t
#What if you wanted to actually have backslashes in the string?
  w="This is a string\\nwith a backslash in it"
  print w
  print "\n\n"
#
#
#
#We can also read a string from the keyboard
  x=raw_input("Enter your own string here")
  print x
  print "\n\n"
#
#Here is how to find the length of a string:
  print len(s)
  print len(u)
#
#There is an empty string!
  e=""
  print "The length of the empty string is\t",len(e),"\n\n\n"
#You can loop through a string with the for statement
  for c in s:
    print c
  print"\n\n\n"
#
#
#
#
#You can use the ord function to get the ASCII code for a character
  print "The ASCII code for 'A' is ", ord("A")
  print "\n\n"
  for c in u:
    print ord(c)
#You can use chr to invert ord
  print "\n\nThe character whose ASCII code is 87 is ", chr(87)
  print "\n\n"
#We can refer to the individual characters in the string using
#bracket notation
  print "cell 0 of s contains", s[0]
  print "cell 1 of s contains", s[1]
#This one will cause an error, so we comment it out!
  #print "cell 5 of s contains", s[5]
  print "\n\n"
#We can use negative indices
  print "cell -1 of s contains", s[-1]
  print "\n\n"
#We can also extract various substrings:
  a=s[1:4]
  b=s[1:5]
  c=s[:4]
  d=s[1:]
  e=s[:-1]
  f=s[-2:]
  print a
  print b
  print c
  print d
  print e
  print f
  print"\n\n"
 #We can use the operator in as part of logical expressions
  if "ood" in t:
    print "'ood' appears in 'goodbye'"
  print "\n\n"
#You CAN'T do this:
  #s[3]='M'
#Instead you have to write
  s=s[0:3]+'M'+s[4:]
  print s