my_list = [3, 2, 1, 1, 2, 3]
print my_list
# [3, 2, 1, 1, 2, 3]
unique_list = list(set(my_list))
print unique_list
# [1, 2, 3]

from collections import OrderedDict


my_list = [3, 2, 1, 1, 2, 3]
print my_list
# [3, 2, 1, 1, 2, 3]
unique_list = list(OrderedDict.fromkeys(my_list))
print unique_list
# [3, 2, 1]

url_dict = {
  'google': 'https://www.google.com/',
  'github': 'https://github.com/',
  'facebook': 'https://www.facebook.com/',
}


print url_dict['facebook']
print url_dict['google']
print url_dict['github']
# print url_dict['baidu']
# KeyError: 'baidu'

# https://www.facebook.com/
# https://www.google.com/
# https://github.com/

url_dict = {
  'google': 'https://www.google.com/',
  'github': 'https://github.com/',
  'facebook': 'https://www.facebook.com/',
}

print url_dict.get('facebook', 'https://www.google.com/')
print url_dict.get('google', 'https://www.google.com/')
print url_dict.get('github', 'https://www.google.com/')
print url_dict.get('baidu', 'https://www.google.com/')

# https://www.facebook.com/
# https://www.google.com/
# https://github.com/
# https://www.google.com/

unordered_dict = {'c': 1, 'b': 2, 'a': 3}

print sorted(unordered_dict.items(), key=lambda e: e[1])
# [('c', 1), ('b', 2), ('a', 3)]

print sorted(unordered_dict.items(), key=lambda e: e[0])
# [('a', 3), ('b', 2), ('c', 1)]

print sorted(unordered_dict.items(), key=lambda e: e[1], reverse=True)
# [('a', 3), ('b', 2), ('c', 1)]