''' Purpose: remind you about string indexing.
             introduce string slicing
'''

# operator [] is the sequence index operator. Our use so far
# is to get an individual character from a string

s = input( 'Enter favorite pie: ' )

t = input( 'Enter two indices: ' )

i, j = t.split()            # i = the first index, j = the second index
i, j = int( i ), int( j )

print( 's:', s )
print( 'i:', i )
print( 'j:', j )

print()

# string indexing: some_string[ index ] --> returns character at position index
# where index is an int in range 0 --> len(some_string) - 1
print( 's[ i ]: ', s[ i ] )
print( 's[ j ]: ', s[ j ] )

print()

# get slices of s using the slicing operator :
# get a substring starting from position i and go up to but not including the character at index j
# so includes character at position i and up to index j - 1
# if i = 3 and j = 15 --> includes all characters starting from index 3 through character at index 14
slice1 = s[ i : j + 1 ]   # we store the substring in a variable so we can use it later
# the second number after : is optional. If you don't give it a second number, then it goes all the way to
# the end of the string s
slice2 = s[ i : ]
# also optional to put a number in front of : --> then start at the very beginning (0) and up to
# but not including j
slice3 = s[ : j ]
# also both numbers are optional --> makes a new copy of the entire string! Starts at index 0 and goes up to
# the end of the string s
slice4 = s[ : ]

# i and j are just variables that hold integers
# we can substitute them for actual numbers

# if s = 'apple'
# index   01234
# s[ 1 : 3 ] = 'pp'
# s[ : 3 ] = 'app'
# s[ 1 : ] = 'pple'
# s[ : ] = 'apple'

# strings are immutable! Cannot change anything, only return a new copy

print( 's[ i : j + 1 ]:', slice1 )
print( 's[ i :   ]:', slice2 )
print( 's[   : j ]:', slice3 )
print( 's[   :   ]:', slice4 )

# to include j, you can do j + 1 in the substring slicing

# if i = 0 and j = 0
#   s[ i : j ] --> goes up to but not including 0 is just an '' because doesn't include 0!