# use slicing to spell a string in reverse 
 
str1 = "Winners never quit, quitters never win!"
# slicing uses [begin : end : step]
# end is exclusive
# defaults are begin = 0, end = len of string, step = 1
# use step = -1 to step from end 
print( "reverse = ", str1[::-1] )

# use slicing to spell a string in reverse 
 
str1 = "Winners never quit, quitters never win!"
# slicing uses [begin : end : step]
# end is exclusive
# defaults are begin = 0, end = len of string, step = 1
# use step = -1 to step from end 
print( "reverse = ", str1[::-1] )
 
# optional wait for keypress
raw_input('Press Enter...')
# with Python3 'raw_input()' has become 'input()'

# slicing uses [start:<end:step]
 
s4 = "hippopotamus"
 
print( "first 2 char = ", s4[0:2] )
print( "next 2 char  = ", s4[2:4] )
print( "last 2 char  = ", s4[-2:] )
print( "exclude first 3 char  = ", s4[3: ] )
print( "exclude last 4 char   = ", s4[:-4] )
print( "reverse the string    = ", s4[::-1] )  # step is -1
print( "the whole word again  = ", s4 )
print( "spell skipping 2 char = ", s4[::2] )  # step is 2
"""
my output -->
first 2 char =  hi
next 2 char  =  pp
last 2 char  =  us
exclude first 3 char  =  popotamus
exclude last 4 char   =  hippopot
reverse the string    =  sumatopoppih
the whole word again  =  hippopotamus
spell skipping 2 char =  hpooau
"""

# exploring Python's slicing operator
# can be used with any indexed sequence like strings, lists, ...
# syntax --> seq[begin : end : step]
# step is optional
# defaults are index begin=0, index end=len(seq)-1, step=1
# -begin or -end --> count from the end backwards
# step = -1 reverses sequence
# if you feel lost, put in the defaults in your mind
 
# use a list as a test sequence
a = [0, 1, 2, 3, 4, 5, 6, 7, 8]
 
print( a[3:6] )   # [3,4,5]
# if either index is omitted, beginning or end of sequence is assumed 
print( a[:3] )    # [0,1,2]
print( a[5:] )    # [5,6,7,8]
 
# negative index is taken from the end of the sequence
print( a[2:-2] )  # [2,3,4,5,6]
print( a[-4:] )   # [5,6,7,8]
 
# extract every second element
print( a[::2] )   # [0, 2, 4, 6, 8]
 
# step=-1 will reverse the sequence
print( a[::-1] )  # [8, 7, 6, 5, 4, 3, 2, 1, 0]
 
# no indices just makes a copy (which is sometimes useful)
b = a[:]
print( b )    # [0, 1, 2, 3, 4, 5, 6, 7, 8]
 
# slice in (replace) an element at index 3
b[3:4] = [100]
print( b )    # [0, 1, 2, 100, 4, 5, 6, 7, 8]
# make another copy, since b has changed
b = a[:]
 
# slice in (insert) a few elements starting at index 3
b[3:] = [9, 9, 9, 9] + b[3:]
print( a )    # [0, 1, 2, 3, 4, 5, 6, 7, 8]
print( b )    # [0, 1, 2, 9, 9, 9, 9, 3, 4, 5, 6, 7, 8]