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Get names of all keys in the collection
...You could do this with MapReduce:
mr = db.runCommand({
"mapreduce" : "my_collection",
"map" : function() {
for (var key in this) { emit(key, null); }
},
"reduce" : function(key, stuff) { return null; },
"out": "my_collection" + "_keys"
})
Then run distinct on the resulting collecti...
“is” operator behaves unexpectedly with integers
...tively rare. Here's an example (will work in Python 2 and 3) e.g.
SENTINEL_SINGLETON = object() # this will only be created one time.
def foo(keyword_argument=None):
if keyword_argument is None:
print('no argument given to foo')
bar()
bar(keyword_argument)
bar('baz')
def b...
Recursively remove files
Does anyone have a solution to remove those pesky ._ and .DS_Store files that one gets after moving files from a Mac to A Linux Server?
...
How should I structure a Python package that contains Cython code
...od relies on the fact that building a .pyx file with Cython.Distutils.build_ext (at least with Cython version 0.14) always seems to create a .c file in the same directory as the source .pyx file.
Here is a cut-down version of setup.py which I hope shows the essentials:
from distutils.core import s...
MySQL query String contains
...
Quite simple actually:
mysql_query("
SELECT *
FROM `table`
WHERE `column` LIKE '%{$needle}%'
");
The % is a wildcard for any characters set (none, one or many). Do note that this can get slow on very large datasets so if your database grows you'll nee...
How to limit the amount of concurrent async I/O operations?
...hecker
{
private const int ThreadCount=20;
private CountdownEvent _countdownEvent;
private SemaphoreSlim _throttler;
public Task Check(IList<string> urls)
{
_countdownEvent = new CountdownEvent(urls.Count);
_throttler = new SemaphoreSlim(ThreadCount);
...
How do I pass a variable by reference?
...le type
Let's try to modify the list that was passed to a method:
def try_to_change_list_contents(the_list):
print('got', the_list)
the_list.append('four')
print('changed to', the_list)
outer_list = ['one', 'two', 'three']
print('before, outer_list =', outer_list)
try_to_change_list_...
Is it expensive to use try-catch blocks even if an exception is never thrown?
...
public class TryFinally {
public TryFinally();
Code:
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]) throws java.lang.Throwable;
Code:
0: new #2 ...
What is Bit Masking?
...esult: 00000101b
Masking is implemented using AND, so in C we get:
uint8_t stuff(...) {
uint8_t mask = 0x0f; // 00001111b
uint8_t value = 0x55; // 01010101b
return mask & value;
}
Here is a fairly common use-case: Extracting individual bytes from a larger word. We define the high-...
Xcode/Simulator: How to run older iOS version?
...
To add previous iOS simulator to Xcode 4.2, you need old xcode_3.2.6_and_ios_sdk_4.3.dmg (or similar version) installer file and do as following:
Mount the xcode_3.2.6_and_ios_sdk_4.3.dmg file
Open mounting disk image and choose menu: Go->Go to Folder...
Type /Volumes/Xcode and iOS...