The usage of OrderedDict in python is explained in detail

Many people think that the dictionary in python is unordered because it is stored as hash, but there is a module in python called collections(English, collection, collection) that comes with a subclass

OrderedDict, which sorts the elements in the dictionary object. See the following example:

import collections
print "Regular dictionary"
d={}
d['a']='A'
d['b']='B'
d['c']='C'
for k,v in d.items():
  print k,v

print "\nOrder dictionary"
d1 = collections.OrderedDict()
d1['a'] = 'A'
d1['b'] = 'B'
d1['c'] = 'C'
d1['1'] = '1'
d1['2'] = '2'
for k,v in d1.items():
  print k,v

Output:

Regular dictionary
a A
c C
b B

Order dictionary
a A
b B
c C
1 1
2 2

As you can see, several elements such as ABC are also saved, but OrderedDict is sorted according to the order in which the elements are put. So the output values are sorted.

The dictionary objects of the OrderedDict object, if they are in a different order, then Python will also treat them as two different objects. See the example:

print 'Regular dictionary:'
d2={}
d2['a']='A'
d2['b']='B'
d2['c']='C'

d3={}
d3['c']='C'
d3['a']='A'
d3['b']='B'

print d2 == d3

print '\nOrderedDict:'
d4=collections.OrderedDict()
d4['a']='A'
d4['b']='B'
d4['c']='C'

d5=collections.OrderedDict()
d5['c']='C'
d5['a']='A'
d5['b']='B'

print d1==d2

Output:

Regular dictionary:
True

OrderedDict:
False

Here are some more examples:

 dd = {'banana': 3, 'apple':4, 'pear': 1, 'orange': 2}
# According to the key The sorting 
kd = collections.OrderedDict(sorted(dd.items(), key=lambda t: t[0]))
print kd
# In accordance with the value The sorting 
vd = collections.OrderedDict(sorted(dd.items(),key=lambda t:t[1]))
print vd

# The output 
OrderedDict([('apple', 4), ('banana', 3), ('orange', 2), ('pear', 1)])
OrderedDict([('pear', 1), ('orange', 2), ('banana', 3), ('apple', 4)])