Python Coding Challange - Question with Answer (01080925)

 

Let’s break it down step by step:

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Code

from collections import defaultdict
d = defaultdict(list) # default factory = list
d['a'].append(10) # appends 10 to list at key 'a'
print(d['b']) # accessing key 'b'

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Explanation

1. defaultdict(list)

   • This creates a dictionary where every new key automatically starts with a default empty list ([]).

   • If you access a missing key, it doesn’t raise KeyError (like normal dict). Instead, it creates a new entry with [] as the value.

2. d['a'].append(10)

   • Key 'a' doesn’t exist initially, so defaultdict creates it with a new list [].

   • Then 10 is appended.

   • Now d = {'a': [10]}.

3. print(d['b'])

   • Key 'b' doesn’t exist, so defaultdict creates it automatically with a default list() (which is []).

   • Nothing is appended, so it just prints [].

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✅ Final Output

[]

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⚡Key point: defaultdict(list) avoids KeyError by supplying a default empty list for missing keys.

APPLICATION OF PYTHON FOR CYBERSECURITY