大约有 25,000 项符合查询结果（耗时：0.1110秒） [XML]
How to dynamically compose an OR query filter in Django?
...'s say with a list
# of db fields that can change like the following
# list_with_strings = ['dbfield1', 'dbfield2', 'dbfield3']
# init our q objects variable to use .add() on it
q_objects = Q(id__in=[])
# loop trough the list and create an OR condition for each item
for item in list:
q_objects...
Is there a way to access an iteration-counter in Java's for-each loop?
...t variant of for iterates over) even have an index, or even have a defined order (some collections may change the order when you add or remove elements).
See for example, the following code:
import java.util.*;
public class TestApp {
public static void AddAndDump(AbstractSet<String> set, ...
Can Python test the membership of multiple values in a list?
...o sets can sometimes be incredibly wasteful, slowing programs down by many orders of magnitude.
Here are a few benchmarks for illustration. The biggest difference comes when both container and items are relatively small. In that case, the subset approach is about an order of magnitude faster:
>...
How to print SQL statement in codeigniter model
...
To display the query string:
print_r($this->db->last_query());
To display the query result:
print_r($query);
The Profiler Class will display benchmark results, queries you have run, and $_POST data at the bottom of your pages.
To enable the p...
Basic http file downloading and saving to disk in python?
...URLopener is deprecated.
And when used you will get error as below:
url_opener = urllib.URLopener() AttributeError: module 'urllib' has no
attribute 'URLopener'
So, try:
import urllib.request
urllib.request.urlretrieve(url, filename)
...
Print current call stack from a method in Python code
...port traceback
def f():
g()
def g():
for line in traceback.format_stack():
print(line.strip())
f()
# Prints:
# File "so-stack.py", line 10, in <module>
# f()
# File "so-stack.py", line 4, in f
# g()
# File "so-stack.py", line 7, in g
# for line in traceback.form...
Update MongoDB field using value of another field
...; {
requests.push( {
'updateOne': {
'filter': { '_id': document._id },
'update': { '$set': { 'name': document.name } }
}
});
if (requests.length === 500) {
//Execute per 500 operations and re-init
db.collection.bulkWrite(requests)...
What Makes a Method Thread-safe? What are the rules?
...e a complete knowledge of the threading behaviour of the entire program in order to ensure its safety.
Again, look at my example: every method is trivial. It is the way that the methods interact with each other at a "global" level that makes the program deadlock. You can't look at every method and...
What are the details of “Objective-C Literals” mentioned in the Xcode 4.4 release notes?
...
This part is new. Expression Literals
When you have an expression (M_PI / 16 for example) you should put it inside parenthesis.
This syntax works for numeral expressions, booleans, finding an index in a (C-) string, boolean values, enum constants, and even character strings!
NSNumber *piO...
What is the use of having destructor as private?
...e connection being open or a file being written. You could have a "request_delete" method in the class or the manager that will check that condition and it will either delete or decline, and return a status telling you what it did. That's far more flexible that just calling "delete".
...