functools | 易学教程

Make @lru_cache ignore some of the function arguments

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问题 How can I make @functools.lru_cache decorator ignore some of the function arguments with regard to caching key? For example, I have a function that looks like this: def find_object(db_handle, query): # (omitted code) return result If I apply lru_cache decorator just like that, db_handle will be included in the cache key. As a result, if I try to call the function with the same query , but different db_handle , it will be executed again, which I'd like to avoid. I want lru_cache to consider

How does functools partial do what it does?

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I am not able to get my head on how the partial works in functools. I have the following code from here : >>> sum = lambda x, y : x + y >>> sum(1, 2) 3 >>> incr = lambda y : sum(1, y) >>> incr(2) 3 >>> def sum2(x, y): return x + y >>> incr2 = functools.partial(sum2, 1) >>> incr2(4) 5 Now in the line incr = lambda y : sum(1, y) I get that whatever argument I pass to incr it will be passed as y to lambda which will return sum(1, y) i.e 1 + y . I understand that. But I didn't understand this incr2(4) . How does the 4 gets passed as x in partial function? To me, 4 should replace the sum2 . What is

How does functools partial do what it does?

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问题 I am not able to get my head on how the partial works in functools. I have the following code from here: >>> sum = lambda x, y : x + y >>> sum(1, 2) 3 >>> incr = lambda y : sum(1, y) >>> incr(2) 3 >>> def sum2(x, y): return x + y >>> incr2 = functools.partial(sum2, 1) >>> incr2(4) 5 Now in the line incr = lambda y : sum(1, y) I get that whatever argument I pass to incr it will be passed as y to lambda which will return sum(1, y) i.e 1 + y . I understand that. But I didn\'t understand this

What does functools.wraps do?

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问题 In a comment on this answer to another question, someone said that they weren\'t sure what functools.wraps was doing. So, I\'m asking this question so that there will be a record of it on StackOverflow for future reference: what does functools.wraps do, exactly? 回答1: When you use a decorator, you're replacing one function with another. In other words, if you have a decorator def logged(func): def with_logging(*args, **kwargs): print(func.__name__ + " was called") return func(*args, **kwargs)