this question has answer here: java inner class , static nested class 23 answers i came across in java, know static nested class why create instance of 'static'. isn't whole idea of 'static' use without instance? understand concept of inner classes, why (and frankly how possible to) create 'instance' of 'static' member @ ? why this: 1- outerclass.staticnestedclass nestedobject = new outerclass.staticnestedclass(); 2- nestedobject.anestedclassmethod(); and not this: 1- outerclass outerinstance=new outerclass(); 2- outerinstance.staticnestedclass.anestedclassmethod(); use on inner classes, keyword static indicates can access inner class without instance of outer class. for example: public class outer { public static class inner { /* code here. */ } } with construction, can create instance of inn...
i have data frame 2 columns: product_id , rating. i'm trying join 2 tables. 1 obtained from a = data.groupby('product_id').count() the other one b = data.groupby('product_id').mean() i'd have table has on columns the product_id count mean try: data.groupby('product_id').agg(['mean', 'count'])
i not sure when use pool of workers vs multiple processes. processes = [] m in range(1,5): p = process(target=some_function) p.start() processes.append(p) p in processes: p.join() vs if __name__ == '__main__': # start 4 worker processes pool(processes=4) pool: pool_outputs = pool.map(another_function, inputs) as says on pymotw : the pool class can used manage fixed number of workers simple cases work done can broken , distributed between workers independently. the return values jobs collected , returned list. the pool arguments include number of processes , function run when starting task process (invoked once per child). please have @ examples given there better understand application, functionalities , parameters. basically pool helper, easing management of processes (workers) in cases need consume common input data, process in parallel , produce joint output. the pool quite few thi...
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