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Underscore.
>>> 5+5
10
>>> _
10
>>> _ + 5
15
>>> _
15
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Weighted random numbers
...er is less than that item's weight
Pseudo-code illustrating this:
int sum_of_weight = 0;
for(int i=0; i<num_choices; i++) {
sum_of_weight += choice_weight[i];
}
int rnd = random(sum_of_weight);
for(int i=0; i<num_choices; i++) {
if(rnd < choice_weight[i])
return i;
rnd -= choic...
How can I add reflection to a C++ application?
...re are some handy macros to help with typed expressions:
#define REM(...) __VA_ARGS__
#define EAT(...)
// Retrieve the type
#define TYPEOF(x) DETAIL_TYPEOF(DETAIL_TYPEOF_PROBE x,)
#define DETAIL_TYPEOF(...) DETAIL_TYPEOF_HEAD(__VA_ARGS__)
#define DETAIL_TYPEOF_HEAD(x, ...) REM x
#define DETAIL_TYP...
When should iteritems() be used instead of items()?
... more like a set (which you'd expect from a dict).
Simple example:
common_keys = list(dict_a.viewkeys() & dict_b.viewkeys())
Will give you a list of the common keys, but again, in Python 3.x - just use .keys() instead.
Python 3.x has generally been made to be more "lazy" - i.e. map is now e...
PHP Pass variable to next page
...n cookies. More secure, but not completely secure.
Session:
//On page 1
$_SESSION['varname'] = $var_value;
//On page 2
$var_value = $_SESSION['varname'];
Remember to run the session_start(); statement on both these pages before you try to access the $_SESSION array, and also before any output i...
Javascript replace with reference to matched group?
I have a string, such as hello _there_ . I'd like to replace the two underscores with <div> and </div> respectively, using JavaScript . The output would (therefore) look like hello <div>there</div> . The string might contain multiple pairs of underscores.
...
Repeat string to certain length
...
def repeat_to_length(string_to_expand, length):
return (string_to_expand * ((length/len(string_to_expand))+1))[:length]
For python3:
def repeat_to_length(string_to_expand, length):
return (string_to_expand * (int(length/len(s...
Django ManyToMany filter()
...
Just restating what Tomasz said.
There are many examples of FOO__in=... style filters in the many-to-many and many-to-one tests. Here is syntax for your specific problem:
users_in_1zone = User.objects.filter(zones__id=<id1>)
# same thing but using in
users_in_1zone = User.object...
What's the difference between django OneToOneField and ForeignKey?
...)
>>> e2 = Engine2.objects.get(name='Wankel')
>>> e2.car2_set.all()
[<Car2: Mazda>]
Model Code
from django.db import models
class Engine(models.Model):
name = models.CharField(max_length=25)
def __unicode__(self):
return self.name
class Car(models.Model)...
Regex lookahead, lookbehind and atomic groups
...pression.info for more details.
Positive lookahead:
Syntax:
(?=REGEX_1)REGEX_2
Match only if REGEX_1 matches; after matching REGEX_1, the match is discarded and searching for REGEX_2 starts at the same position.
example:
(?=[a-z0-9]{4}$)[a-z]{1,2}[0-9]{2,3}
REGEX_1 is [a-z0-9]{4}$ which...