大约有 7,000 项符合查询结果（耗时：0.0262秒） [XML]
Setting an object to null vs Dispose()
...cts which are no longer reachable, but which have a finalizer (written as ~Foo() in C#, somewhat confusingly - they're nothing like C++ destructors). It runs the finalizers on these objects, just in case they need to do extra cleanup before their memory is freed.
Finalizers are almost always used t...
Replacing blank values (white space) with NaN in pandas
...e() does the job, since pandas 0.13:
df = pd.DataFrame([
[-0.532681, 'foo', 0],
[1.490752, 'bar', 1],
[-1.387326, 'foo', 2],
[0.814772, 'baz', ' '],
[-0.222552, ' ', 4],
[-1.176781, 'qux', ' '],
], columns='A B C'.split(), index=pd.date_range('2000-01-01','...
How to retrieve inserted id after inserting row in SQLite using Python?
...nect(':memory:')
cursor=connection.cursor()
cursor.execute('''CREATE TABLE foo (id integer primary key autoincrement ,
username varchar(50),
password varchar(50))''')
cursor.execute('INSERT INTO foo (username,password) VALUES (?...
Why is Class.newInstance() “evil”?
... this very simple class (does not matter that it is broken):
static class Foo {
public Foo() throws IOException {
throw new IOException();
}
}
And you try to create an instance of it via reflection. First Class::newInstance:
Class<Foo> clazz = ...
try {
cla...
Why does flowing off the end of a non-void function without returning a value not produce a compiler
... as a curiosity, look what this code does:
#include <iostream>
int foo() {
int a = 5;
int b = a + 1;
}
int main() { std::cout << foo() << std::endl; } // may print 6
This code has formally undefined behaviour, and in practice it's calling convention and architecture depe...
How to flush output of print function?
...ust provide flush=True as a keyword argument to the print function:
print('foo', flush=True)
Python 2 (or < 3.3)
They did not backport the flush argument to Python 2.7 So if you're using Python 2 (or less than 3.3), and want code that's compatible with both 2 and 3, may I suggest the following ...
Spring Data JPA - “No Property Found for Type” Exception
...re was an interface defined for the old property name.
public interface IFooDAO extends JpaRepository< Foo, Long >{
Foo findByOldPropName( final String name );
}
The error indicated that it could no longer find "OldPropName" and threw the exception.
To quote the article on DZone:
...
How can I add an item to a IEnumerable collection?
...lOrEmpty(s));
}
IEnumerable<string> lines = ReadLines();
lines.Add("foo") // so what is this supposed to do??
What you can do, however, is create a new IEnumerable object (of unspecified type), which, when enumerated, will provide all items of the old one, plus some of your own. You use Enu...
What would be C++ limitations compared C language? [closed]
...itrary subset of C++. C is not a subset of C++ at all.
This is valid C:
foo_t* foo = malloc ( sizeof(foo_t) );
To make it compile as C++ you have to write:
foo_t* foo = static_cast<foo_t*>( malloc ( sizeof(foo_t) ) );
which isn't valid C any more. (you could use the C-style cast, it wh...
Difference between clustered and nonclustered index [duplicate]
... index). For example, if you have the query (in pseudocode)
SELECT * FROM FOO WHERE FOO.BAR = 2
You might want to put an index on FOO.BAR. A clustered index should be used on a column that will be used for sorting. A clustered index is used to sort the rows on disk, so you can only have one per t...