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“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...
Adding new column to existing DataFrame in Python pandas
...17438 0.847941 0.034235 -0.448948 2.228131
>>> p.version.short_version
'0.16.1'
The SettingWithCopyWarning aims to inform of a possibly invalid assignment on a copy of the Dataframe. It doesn't necessarily say you did it wrong (it can trigger false positives) but from 0.13.0 it let yo...
e.printStackTrace equivalent in python
...
import traceback
traceback.print_exc()
When doing this inside an except ...: block it will automatically use the current exception. See http://docs.python.org/library/traceback.html for more information.
...
Node.js / Express.js - How does app.router work?
...r middleware is given to use first.
If you do this:
app.use(express.static(__dirname + '/public'));
app.use(app.router);
Then the file on disk is served.
If you do it the other way,
app.use(app.router);
app.use(express.static(__dirname + '/public'));
Then the route handler gets the request, and "H...
How to identify if the DLL is Debug or Release build (in .NET) [duplicate]
...wered Apr 28 '09 at 17:15
this. __curious_geekthis. __curious_geek
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...
NSNotificationCenter addObserver in Swift
...erver(self, selector: #selector(YourClassName.methodOfReceivedNotification(_:)), name:"NotificationIdentifier", object: nil)
Method handler for received Notification
func methodOfReceivedNotification(notification: NSNotification){
// Take Action on Notification
}
For historic Xcode versio...
Getting a better understanding of callback functions in JavaScript
...epending how you call the function
alert(this);
};
callback(argument_1, argument_2);
callback.call(some_object, argument_1, argument_2);
callback.apply(some_object, [argument_1, argument_2]);
The method you choose depends whether:
You have the arguments stored in an Array or as distinct v...
Reverse a string in Python
... for readability and reusability, put the slice in a function
def reversed_string(a_string):
return a_string[::-1]
and then:
>>> reversed_string('a_string')
'gnirts_a'
Longer explanation
If you're interested in the academic exposition, please keep reading.
There is no built-i...
How to hash some string with sha256 in Java?
...onvert the string into bytes (e.g. using text.getBytes(StandardCharsets.UTF_8)) and then hash the bytes. Note that the result of the hash would also be arbitrary binary data, and if you want to represent that in a string, you should use base64 or hex... don't try to use the String(byte[], String) co...
Best practices for in-app database migration for Sqlite
...t/set this variable with the following sqlite statements:
> PRAGMA user_version;
> PRAGMA user_version = 1;
When the app starts, I check the current user-version, apply any changes that are needed to bring the schema up to date, and then update the user-version. I wrap the updates in a t...