Python Notes

Magic Methods

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Method	Purpose	Example Usage
__init__	Initializes object attributes during instantiation.	p = Person("Alice", 25)
__lt__	Defines behavior for < operator for custom objects.	print(n1 < n2)
__str__	Returns a human-readable string representation of an object.	print(p) or str(p)

• Methods starting and ending with double underscores. They are defined by built-in classes in Python and commonly used for operator overloading
• For more examples, see docs

Count Occurrences of Elements

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from collections import Counter
 
# Count characters in a string
Counter("banana")
# Output: Counter({'a': 3, 'n': 2, 'b': 1})
 
# Count characters in a string
Counter([1, 2, 2, 3, 3, 3])
# Output: Counter({3: 3, 2: 2, 1: 1})
 
# Most Common Elements
Counter([1,1,1,2,2,3,4,5,6]).most_common(2)
# Output: [(1, 3), (2, 2)]

Throwaway Variable

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for _ in range(k):
	print("This will print k times")

• _ is the throwaway variable. This is a way to indicate to other developers that the loop variable is intentionally not going to be used.