''' Purpose: Remind you about subscript indexing.
            Introduce slicing
'''

# operator [] is the sequence index operator. Our use so far in strings is to
# get an individual character; and in lists to get an individual element value

s = 'of to in is on by it or be at'
words = s.split()

print( 's =', s )
print( 'words =', words )

print()

# get the middle charcter in string s
ns = len( s )

i  = ns // 2

mid_ch = s[ i ]

# get the middle word in the list w

nw = len( words )

i = nw // 2

middle_word= words[ i ]

# operator [] can also be used to get a slice (substring) of a string and a
# sublist of a list

# get the middle half, 1st three quarters, last 3 quarters, and a copy

i1 = ns // 4
i2 = 3 * ns // 4

s1 = s[ i1 : i2 ]
s2 = s[    : i2 ]
s3 = s[ i1 :    ]
s4 = s[    :    ]

print( 's[', i1, ':', i2, ']  =', s1 )
print( 's[   :',     i2, ']  =', s2 )
print( 's[', i1, ':    ]  =',     s3 )
print( 's[   :    ]  =',         s4 )


print()

# get the middle 3 fifths, 1st 4 fifths, last 4 fifths, and a copy

j1 = nw // 5
j2 = 4 * nw // 5

w_slice1 = words[ j1 : j2 ]
w_slice2 = words[    : j2 ]
w_slice3 = words[ j1 :    ]
w_slice4 = words[    :    ]

print( 'words[', j1, ':', j2, ']  =', w_slice1 )
print( 'words[   :',     j2, ']  =', w_slice2 )
print( 'words[', j1, ':   ]  =',     w_slice3 )
print( 'words[   :   ]  =',         w_slice4 )