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Editor to share with you how python access the Dict dictionary, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's learn about it!

Access Dict Dictionary

You will also often write key,value (key, value) to dicts.

If you try to access a key that does not exist in dict, you may be inclined to do this to avoid KeyError errors:

Countr = {} bag = [2, 3, 1, 2, 5, 6, 7, 9, 2, 7] for i in bag: if i in countr: countr [I] + = 1 else: countr [I] = 1for i in range (10): if i in countr: print ("Count of {}: {}" .format (I, format [I)) else: print ("Count of {}: {}" .format (I, 0))

However, using get () is a better approach.

Countr = {} bag = [2,3,1,2,5,6,7,9,2,7] for i in bag: countr [I] = countr.get (I, 0) + 1for i in range (10): print ("Count of {}: {}" .format (I, countr.get (I, 0)

Of course, you can use setdefault instead.

This is also done in a simpler but more expensive way:

Bag = [2, 3, 1, 2, 5, 6, 7, 9, 2, 7] # {2: 3, 3: 1, 1: 1, 5: 1, 6: 1, 7: 2, 9: 1} countr = dict ([(num, bag.count (num) for num in bag]) for i in range (10): print ("Count of {}: {}" .format (I, countr.get (0)

You can also use dict deduction.

Countr = {num: bag.count (num) for num in bag}

These two methods are expensive because they traverse the list each time count is called.

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