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What is the purpose of python's inner classes?
...
Quoted from http://www.geekinterview.com/question_details/64739:
Advantages of inner class:
Logical grouping of classes: If a class is useful to only one other class then it is logical to embed it in that class and keep the two together. Nesting such "helper cla...
Export specific rows from a PostgreSQL table as INSERT SQL script
...le with the set you want to export and then use the command line utility pg_dump to export to a file:
create table export_table as
select id, name, city
from nyummy.cimory
where city = 'tokyo'
$ pg_dump --table=export_table --data-only --column-inserts my_database > data.sql
--column-insert...
How do I find the location of Python module sources?
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For a pure python module you can find the source by looking at themodule.__file__.
The datetime module, however, is written in C, and therefore datetime.__file__ points to a .so file (there is no datetime.__file__ on Windows), and therefore, you can't see the source.
If you download a python sour...
Why do we need extern “C”{ #include } in C++?
...the prototype as a C function, the C++ will actually generate code calling _Zprintf, plus extra crap at the end.)
So: use extern "C" {...} when including a c header—it's that simple. Otherwise, you'll have a mismatch in compiled code, and the linker will choke. For most headers, however, you won'...
Programmatically change UITextField Keyboard type
...
_textField .keyboardType = UIKeyboardTypeAlphabet;
_textField .keyboardType = UIKeyboardTypeASCIICapable;
_textField .keyboardType = UIKeyboardTypeDecimalPad;
_textField .keyboardType = UIKeyboardTypeDefault;
_textField .keyb...
addEventListener not working in IE8
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Try:
if (_checkbox.addEventListener) {
_checkbox.addEventListener("click", setCheckedValues, false);
}
else {
_checkbox.attachEvent("onclick", setCheckedValues);
}
Update::
For Internet Explorer versions prior to IE9, attach...
What is the difference between char s[] and char *s?
...So:
char *x = "Foo";
// is approximately equivalent to:
static const char __secret_anonymous_array[] = "Foo";
char *x = (char *) __secret_anonymous_array;
Note that you must not ever attempt to modify the contents of this anonymous array via this pointer; the effects are undefined (often meaning ...
How can I use “sizeof” in a preprocessor macro?
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Following snippets will produce no code if sizeof(someThing) equals PAGE_SIZE; otherwise they will produce a compile-time error.
1. C11 way
Starting with C11 you can use static_assert (requires #include <assert.h>).
Usage:
static_assert(sizeof(someThing) == PAGE_SIZE, "Data structure do...
“Private” (implementation) class in Python
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Use a single underscore prefix:
class _Internal:
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This is the official Python convention for 'internal' symbols; "from module import *" does not import underscore-prefixed objects.
Edit: Reference to the single underscore convention
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Convert an image (selected by path) to base64 string
...e to retrieve the base64 string
public static string ImageToBase64(string _imagePath)
{
string _base64String = null;
using (System.Drawing.Image _image = System.Drawing.Image.FromFile(_imagePath))
{
using (MemoryStream _mStream = new MemoryStream())
...