大约有 46,000 项符合查询结果（耗时：0.0535秒） [XML]
Simulate CREATE DATABASE IF NOT EXISTS for PostgreSQL?
...an work around it from within psql by executing the DDL statement conditionally:
SELECT 'CREATE DATABASE mydb'
WHERE NOT EXISTS (SELECT FROM pg_database WHERE datname = 'mydb')\gexec
The manual:
\gexec
Sends the current query buffer to the server, then treats each column of each row of the query's...
How does collections.defaultdict work?
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Usually, a Python dictionary throws a KeyError if you try to get an item with a key that is not currently in the dictionary. The defaultdict in contrast will simply create any items that you try to access (provided of course th...
How to read a file in reverse order?
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– BringBackCommodore64
Mar 13 '17 at 16:09
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show 5 more co...
Is there a performance difference between i++ and ++i in C++?
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However, if i is an instance of a C++ class, then i++ and ++i are making calls to one of the operator++ functions. Here's a standard pair of these functions:
Foo& Foo::operator++() // called for ++i
{
this->data += 1;
return *this;
}
Foo Foo::operator++(int ignored_dummy_value) ...
Downloading a picture via urllib and python
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Note for Python 3 it's actually import urllib.request urllib.request.urlretrieve("http://...jpg", "1.jpg"). It's urlretrieve now as of 3.x.
– user1032613
Mar 16 '18 at 0:18
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What is a callback function?
What is a callback function?
21 Answers
21
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Understanding Apache's access log
...the client IP)
%l is the identity of the user determined by identd (not usually used since not reliable)
%u is the user name determined by HTTP authentication
%t is the time the request was received.
%r is the request line from the client. ("GET / HTTP/1.0")
%>s is the status code sent from the s...
How to provide user name and password when connecting to a network share
...user via explorer?
– Breeze
Mar 21 '16 at 10:06
@Breeze - I haven't tested it, but I'd expect it authenticate for the ...
Fast Linux File Count for a large number of files
...ke a while if there are a lot of them. Also there will be no output until all of the names are read and sorted. Use the ls -f option to turn off sorting.
ls -f | wc -l
Note that this will also enable -a, so ., .., and other files starting with . will be counted.
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Why are function pointers and data pointers incompatible in C/C++?
...ry but C doesn't limit itself to only certain types of architectures if at all possible.
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