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Creating a singleton in Python
This question is not for the discussion of whether or not the singleton design pattern is desirable, is an anti-pattern, or for any religious wars, but to discuss how this pattern is best implemented in Python in such a way that is most pythonic. In this instance I define 'most pythonic' to mean tha...
Access an arbitrary element in a dictionary in Python
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for a non-destructive popitem you can make a (shallow) copy: key, value = dict(d).popitem()
– Pelle
Jan 31 '18 at 10:35
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Do I need to explicitly call the base virtual destructor?
...don't need to call the base destructor, a base destructor is always called for you by the derived destructor. Please see my related answer here for order of destruction.
To understand why you want a virtual destructor in the base class, please see the code below:
class B
{
public:
virtual ~...
How do you add a Dictionary of items into another Dictionary
... add the contents of one Array to another. Is there an easy way to do that for a dictionary?
28 Answers
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Sending multipart/formdata with jQuery.ajax
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Starting with Safari 5/Firefox 4, it’s easiest to use the FormData class:
var data = new FormData();
jQuery.each(jQuery('#file')[0].files, function(i, file) {
data.append('file-'+i, file);
});
So now you have a FormData object, ready to be sent along with the XMLHttpRequest.
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Importing a CSV file into a sqlite3 database table using Python
...` statement available in 2.5+
# csv.DictReader uses first line in file for column headings by default
dr = csv.DictReader(fin) # comma is default delimiter
to_db = [(i['col1'], i['col2']) for i in dr]
cur.executemany("INSERT INTO t (col1, col2) VALUES (?, ?);", to_db)
con.commit()
con.c...
Django in / not in query
I'm trying to figure out how to write a 'not in' style query in django.
For example, the query structure I'm thinking of would look like this.
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How do you use the ellipsis slicing syntax in Python?
...builtin class or Python language constuct makes use of it.
So the syntax for it depends entirely on you, or someone else, having written code to understand it.
Numpy uses it, as stated in the documentation. Some examples here.
In your own class, you'd use it like this:
>>> class TestEl...
How do I calculate square root in Python?
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You have to write: sqrt = x**(1/2.0), otherwise an integer division is performed and the expression 1/2 returns 0.
This behavior is "normal" in Python 2.x, whereas in Python 3.x 1/2 evaluates to 0.5. If you want your Python 2.x code to behave like 3.x w.r.t. division write from __future__ import d...
$_POST vs. $_SERVER['REQUEST_METHOD'] == 'POST'
... request method (surprise).
$_POST contains any post data.
It's possible for a POST request to contain no POST data.
I check the request method — I actually never thought about testing the $_POST array. I check the required post fields, though. So an empty post request would give the user a lot...