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Difference between Python's Generators and Iterators
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iterator is a more general concept: any object whose class has a __next__ method (next in Python 2) and an __iter__ method that does return self.
Every generator is an iterator, but not vice versa. A generator is built by calling a function that has one or more yield expressions (yield st...
Ignore python multiple return value
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One common convention is to use a "_" as a variable name for the elements of the tuple you wish to ignore. For instance:
def f():
return 1, 2, 3
_, _, x = f()
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What is the most efficient way of finding all the factors of a number in Python?
...om functools import reduce
def factors(n):
return set(reduce(list.__add__,
([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0)))
This will return all of the factors, very quickly, of a number n.
Why square root as the upper limit?
sqrt(x) * sqrt(x) = x. So if t...
How to watch for array changes?
...ods or the length property).
function ObservableArray(items) {
var _self = this,
_array = [],
_handlers = {
itemadded: [],
itemremoved: [],
itemset: []
};
function defineIndexProperty(index) {
if (!(index in _self)) {
Object.defineProperty...
How do I get Flask to run on port 80?
...link to the official documentation about setting up Flask with Apache + mod_wsgi.
Edit 1 - Clarification for @Djack
Proxy HTTP traffic to Flask through apache2
When a request comes to the server on port 80 (HTTP) or port 443 (HTTPS) a web server like Apache or Nginx handles the connection of ...
What does the “yield” keyword do?
...ou create the method of the node object that will return the generator
def _get_child_candidates(self, distance, min_dist, max_dist):
# Here is the code that will be called each time you use the generator object:
# If there is still a child of the node object on its left
# AND if the d...
Can a dictionary be passed to django models on create?
...our model is called MyModel:
# create instance of model
m = MyModel(**data_dict)
# don't forget to save to database!
m.save()
As for your second question, the dictionary has to be the final argument. Again, extra and extra2 should be fields in the model.
m2 =MyModel(extra='hello', extra2='world'...
How can I tell gcc not to inline a function?
...eing
optimized away, put
asm ("");
Use it like this:
void __attribute__ ((noinline)) foo()
{
...
}
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NSLog the method name with Objective-C in iPhone
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print(__FUNCTION__) // Swift
NSLog(@"%@", NSStringFromSelector(_cmd)); // Objective-C
Swift 3 and above
print(#function)
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Get exception description and stack trace which caused an exception, all as a string
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See the traceback module, specifically the format_exc() function. Here.
import traceback
try:
raise ValueError
except ValueError:
tb = traceback.format_exc()
else:
tb = "No error"
finally:
print tb
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