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#!/usr/bin/env python3

# Copyright 2014 Brett Slatkin, Pearson Education Inc.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

# Preamble to mimick book environment

import logging

from pprint import pprint

from sys import stdout as STDOUT

# Example 1

a = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']

print('First four:', a[:4])

print('Last four: ', a[-4:])

print('Middle two:', a[3:-3])

# Example 2

assert a[:5] == a[0:5]

# Example 3

assert a[5:] == a[5:len(a)]

# Example 4

print(a[:5])

print(a[:-1])

print(a[4:])

print(a[-3:])

print(a[2:5])

print(a[2:-1])

print(a[-3:-1])

# Example 5

a[:] # ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']

a[:5] # ['a', 'b', 'c', 'd', 'e']

a[:-1] # ['a', 'b', 'c', 'd', 'e', 'f', 'g']

a[4:] # ['e', 'f', 'g', 'h']

a[-3:] # ['f', 'g', 'h']

a[2:5] # ['c', 'd', 'e']

a[2:-1] # ['c', 'd', 'e', 'f', 'g']

a[-3:-1] # ['f', 'g']

# Example 6

first_twenty_items = a[:20]

last_twenty_items = a[-20:]

# Example 7

try:

a[20]

except:

logging.exception('Expected')

else:

assert False

# Example 8

b = a[4:]

print('Before: ', b)

b[1] = 99

print('After: ', b)

print('No change:', a)

# Example 9

print('Before ', a)

a[2:7] = [99, 22, 14]

print('After ', a)

# Example 10

b = a[:]

assert b == a and b is not a

# Example 11

b = a

print('Before', a)

a[:] = [101, 102, 103]

assert a is b # Still the same list object

print('After ', a) # Now has different contents