What is Python's comprehension advanced patterns?
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Answer
Python comprehensions extend beyond simple transformations. Nested comprehensions: [[row[i] for row in matrix] for i in range(len(matrix[0]))] transposes a matrix. Conditional expression in output: [x if x > 0 else -x for x in data] (abs value). Walrus operator in comprehensions (Python 3.8+): [y for x in data if (y := process(x)) is not None] — compute once, use twice. Generator pipelines: chain generator expressions for lazy processing: lines = (l.strip() for l in file); non_empty = (l for l in lines if l); results = (parse(l) for l in non_empty). Dict comprehensions from pairs: {v: k for k, v in original.items()} (invert dict). Set comprehension for deduplication: {item.lower() for item in tags}. Comprehensions are single-pass and generally 30-50% faster than equivalent for-loop + append patterns.
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