python - deque example
An OrderedDict is a dictionary subclass that remembers the order
that keys were first inserted. A regular dict doesn’t track the
insertion order, and iterating it gives the values in an arbitrary
order.
# A Python program to demonstrate working of OrderedDict
from collections import OrderedDict
d = {} # regular dict
d['a'] = 1
d['b'] = 2
d['c'] = 3
for key, value in d.items():
print(key, value)
# Output
# ('a', 1)
# ('c', 3)
# ('b', 2)
od = OrderedDict() # Ordered Dict
od['a'] = 1
od['b'] = 2
od['c'] = 3
for key, value in od.items():
print(key, value)
# Output
# ('a', 1)
# ('b', 2)
# ('c', 3)
# It is usefull when dealing with treads
from collections import deque
students = deque(('Sarah', 'Mary', 'Carl'))
students.append('Charlotte') # this name appear at the end of the deque
students.appendleft('Ruth') # this name appear at the start of the deque
students.pop() # remove the element from the end
students.popleft() # remove the element from the start
print(students) 
