script_13.py - List Enumeration

Code

See script_13.py for full code.

Explanation

Line 9: for index, fruit in enumerate(fruits): - enumerate() adds counter to iteration - Returns tuples: (0, "apple"), (1, "banana"), etc. - Tuple unpacking: index gets counter, fruit gets element - Default counter starts at 0

Line 14: for num, fruit in enumerate(fruits, start=1): - start=1 parameter changes starting index - Counter becomes 1, 2, 3, 4 instead of 0, 1, 2, 3 - Useful for human-readable numbering

Line 20: data = ["100", "200", "invalid", "400", "bad"] - Mixed list: some convertible to int, some not

Line 22: def process_number(value): - Function that may raise exception

Line 25-26: Empty lists for results - errors collects error messages - results collects successful conversions

Line 28: for line_num, value in enumerate(data, start=1): - Using enumerate to track position for error reporting - line_num shows which input failed

Line 29-33: Try-except block - try: attempts conversion - except ValueError: catches conversion errors - as e captures exception object

Line 32: errors.append(f"Line {line_num}: Invalid value '{value}'") - Stores error with line number context - Useful for debugging and user feedback

Line 39: positions = [i for i, x in enumerate(numbers) if x == target] - List comprehension with enumerate - Filters to matching elements - Collects their indices - Finds all positions of target value

Line 45: for rank, (name, score) in enumerate(zip(names, scores), start=1): - Combines enumerate with zip - Nested tuple unpacking: (name, score) from zipped pairs - rank from enumerate - Three variables from two functions

Line 51: tag_to_index = {tag: idx for idx, tag in enumerate(tags)} - Dict comprehension with enumerate - Creates reverse index (value -> position) - Useful for lookups