Random examples of list slicing in Python

python-list-slicing-examples.py

# Lists are zero-indexed
# We can provide three-part slices as list[start:stop:step]
# If start is omitted, start at the first item
# If stop is omitted, stop at the last item
# If step is omitted, step by 1

fruits = ['Apple','Orange',
          'Pear','Pineapple',
          'Grape','Berry']

# fruits[start:stop:step]

def labelprint(label,expr):
    print(f"{label}:\n {expr}\n")

labelprint("1st to 3rd",fruits[:3])
# 1st to 3rd:
#  ['Apple', 'Orange', 'Pear']

labelprint("2nd to end",fruits[1:])
# 2nd to end:
#  ['Orange', 'Pear', 'Pineapple', 'Grape', 'Berry']

labelprint("reversed",fruits[::-1])
# reversed:
#  ['Berry', 'Grape', 'Pineapple', 'Pear', 'Orange', 'Apple']

labelprint("Even-indexed",fruits[::2])
# Even-indexed:
#  ['Apple', 'Pear', 'Grape']

labelprint("Odd-indexed",fruits[1::2])
# Odd-indexed:
#  ['Orange', 'Pineapple', 'Berry']

labelprint("Eclude last 2",fruits[:-2])
# Eclude last 2:
#  ['Apple', 'Orange', 'Pear', 'Pineapple']

labelprint("Last 2",fruits[-2:])
# Last 2:
#  ['Grape', 'Berry']

labelprint("Middle 2 - v1",fruits[2:4])
# Middle 2 - v1:
#  ['Pear', 'Pineapple']

labelprint("Middle 2 - v2",fruits[2:-2])
# Middle 2 - v2:
#  ['Pear', 'Pineapple']

labelprint("Every 3rd item starting from the 2nd",fruits[1::3])
# Every 3rd item starting from the 2nd:
#  ['Orange', 'Grape']


labelprint("Every 3rd item starting from the end, backwards",fruits[-1::-3])
# Every 3rd item starting from the end, backwards:
#  ['Berry', 'Pear']

labelprint("First 4 in reverse order",fruits[3::-1])
# First 4 in reverse order:
#  ['Pineapple', 'Pear', 'Orange', 'Apple']

labelprint("First 3 even-indexed",fruits[::2][:3])
# First 3 even-indexed:
#  ['Apple', 'Pear', 'Grape']

labelprint("Every 3rd starting from 2nd, up to but not including last",fruits[1:-1:3])
# Every 3rd starting from 2nd, up to but not including last:
#  ['Orange', 'Grape']