What is a list deduction formula
List Deduction is a concise way to create a list in Python, replacing the traditional for loop append pattern with a single line of code.
Basic grammar
[expression for item in iterable if condition]
Example: Filter even numbers and square them
result = [x**2 for x in range(10) if x % 2 == 0]
Nested deduction formula
Matrix expansion can be achieved:
matrix = [[1,2],[3,4],[5,6]]
performance advantage
The list derivation is about 20% -30% faster than the equivalent for loop because it is implemented by specialized bytecode at the bottom of CPython, avoiding the cost of each append function call.
Precautions
- Avoid nesting more than two layers, otherwise readability will decrease
- Considering generator expressions to save memory under large data volumes
- It is still recommended to use ordinary functions for complex logic
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