Function decorators, generator functions, and the yield keyword, each explained with a short example.
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- What is a Python decorator?
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A function that wraps another function or class to modify its behavior without permanently changing the original.- What does the @ symbol do when placed before a function name?
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It applies a decorator to the function, equivalent to func = decorator(func).- Can multiple decorators be applied to a single function?
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Yes, they can be stacked. They execute from bottom to top when applied.- What is the purpose of functools.wraps in a decorator?
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It preserves the original function's metadata, including __name__ and __doc__, on the wrapper function.- What is a parameterized decorator?
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A decorator that accepts arguments to configure its behavior before decorating the target function.- Write a simple decorator that adds a print statement before a function runs.
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def my_decorator(func): def wrapper(*args, **kwargs): print('Starting'); return func(*args, **kwargs); return wrapper- Can you decorate a class with a decorator?
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Yes, class decorators can modify class attributes, methods, or return an entirely different class.- When two decorators are stacked, which one's wrapper executes first?
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The top decorator's wrapper executes first, but the bottom decorator was applied last to the original function.- Why should a decorator preserve *args and **kwargs?
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To allow the decorator to work with functions of any signature without knowing their exact parameters.- What is a generator function?
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A function that uses the yield keyword to return values one at a time, preserving state between calls.- What does the yield keyword do?
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It pauses the function, returns a value to the caller, and resumes execution from that point on the next call.- What does calling a generator function return?
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A generator object (an iterator), not the first yielded value.- How do you retrieve values from a generator?
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Use next() on the generator object, or iterate over it with a for loop.- What exception is raised when a generator is exhausted?
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StopIteration, indicating no more values are available.- What is a generator expression?
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A generator created inline using syntax like (x**2 for x in range(10)), with parentheses instead of square brackets.
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