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What does functools.wraps do?
...@wim: I've written some decorators which do their own version of @wraps in order to perform various types of modification or annotation on the values copied over. Fundamentally, it's an extension of the Python philosophy that explicit is better than implicit and special cases aren't special enough t...
Why should I use a pointer rather than the object itself?
...y, you shouldn't abuse it. So here are some disadvantages in no particular order:
It is error-prone. Manual memory allocation is dangerous and you are prone to leaks. If you are not proficient at using the debugger or valgrind (a memory leak tool), you may pull your hair out of your head. Luckily ...
View's SELECT contains a subquery in the FROM clause
...y client_id
create view view_credit_status as
select
credit_orders.client_id,
sum(credit_orders.number_of_credits) as purchased,
ifnull(t1.credits_used,0) as used
from credit_orders
left outer join view_clients_credit_usage as t1 on t1.client_id = credit_ord...
css z-index lost after webkit transform translate3d
... So in "preserve-3d" mode we gotta use z-axis of transform to set order, and in flat mode we should use z-index. The bug is that z-index on safari is broken in combination with HW accelerated transforms.
– Steven Lu
Jan 27 '13 at 17:56
...
Why is address zero used for the null pointer?
... code you will still continue to designate null-pointers by constant 0. In order to assign a null-pointer value to a given pointer, you will continue to use expressions like p = 0. It is the compiler's responsibility to realize what you want and translate it into the proper null-pointer value repres...
select * vs select column
...as to what you want, it will first need to check the table's definition in order to determine the columns on that table. That lookup will cost some time - not much in a single query - but it adds up over time
if you need only 2/3 of the columns, you're selecting 1/3 too much data which needs to be r...
Does a foreign key automatically create an index?
...
Say you have a big table called orders, and a small table called customers. There is a foreign key from an order to a customer. Now if you delete a customer, Sql Server must check that there are no orphan orders; if there are, it raises an error.
To check ...
Setting variable to NULL after free
...roblem in such cases is to review and rethink the structure of the code in order to avoid the situation when the same pointer is passed to free more than once. In such cases setting the pointer to NULL and considering the problem "fixed" is nothing more than an attempt to sweep the problem under the...
Finding row index containing maximum value using R
...
See ?order. You just need the last index (or first, in decreasing order), so this should do the trick:
order(matrix[,2],decreasing=T)[1]
share
...
MySQL INNER JOIN select only one row from second table
... = (
SELECT id
FROM payments AS p2
WHERE p2.user_id = u.id
ORDER BY date DESC
LIMIT 1
)
Or
SELECT u.*, p.*
FROM users AS u
INNER JOIN payments AS p ON p.user_id = u.id
WHERE NOT EXISTS (
SELECT 1
FROM payments AS p2
WHERE
p2.user_id = p.user_id AND
(p...