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Going through Python 3's ChainMap
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from collections import ChainMap | |
# Traditionally, you can combine dictionaries into one, | |
# however, this creates a totally new dictionary | |
# e.g. for Python 3.5, you could do this: | |
a = {'name': 'Andela'} | |
b = {'class': 'World'} | |
c = {**a, **b} | |
# Notice, if a or b are updated, (obviously) c does not change | |
# And c, will be using extra memory the size of a + b | |
# With ChainMap | |
d = ChainMap(a, b) | |
print d # ChainMap({'name': 'Andela'}, {'class': 'World'}) | |
print d['name'] # 'Andela' | |
# However, note that ChainMap only creates an interface through which | |
# the specific values of the dictionaries can be accessed. | |
# There's a catch though. If we have duplicate keys with different values, | |
# Only the first one will be picked, e.g. | |
d = ChainMap(a, b, {'name': 'NG'}) | |
print d # 'Andela' | |
d = ChainMap({'name': 'NG'}, a, b} | |
print d # 'NG' | |
# Conclusion: the beauty of ChainMap is in the ability to create | |
# a handy interface through which you can access multiple dictionaries | |
# at once; with minimal extra memory usage. |
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