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What's the (hidden) cost of Scala's lazy val?
...he bitmap indicates it is necessary.
Using:
class Something {
lazy val foo = getFoo
def getFoo = "foo!"
}
produces sample bytecode:
0 aload_0 [this]
1 getfield blevins.example.Something.bitmap$0 : int [15]
4 iconst_1
5 iand
6 iconst_0
7 if_icmpne 48
10 aload_0 [this]
11 dup
12...
How are booleans formatted in Strings in Python?
...he object as transparantly as possible for python. For example, print(str("foo")) merely prints foo on a new line. print(repr("foo")) however prints 'foo' on a new line, including the quotes, since that's what you need to type in the python interpreter to get the corresponding object to the argument...
Defining a variable with or without export
...
Specifically export makes the variable available to child processes via the environment.
– Beano
Jul 21 '09 at 13:35
...
Is it pythonic to import inside functions?
...at it needs to import.
If I'm adding new code to an existing file I'll usually do the import where it's needed and then if the code stays I'll make things more permanent by moving the import line to the top of the file.
One other point, I prefer to get an ImportError exception before any code is r...
What does the explicit keyword mean?
...
The compiler is allowed to make one implicit conversion to resolve the parameters to a function. What this means is that the compiler can use constructors callable with a single parameter to convert from one type to another in order to get t...
MongoDB atomic “findOrCreate”: findOne, insert if nonexistent, but do not update
...: { _id: "some potentially existing id" },
update: {
$setOnInsert: { foo: "bar" }
},
new: true, // return new doc if one is upserted
upsert: true // insert the document if it does not exist
})
As $setOnInsert only affects documents being inserted, if an existing document is found, no...
Stripping everything but alphanumeric chars from a string in Python
What is the best way to strip all non alphanumeric characters from a string, using Python?
11 Answers
...
How to 'bulk update' with Django?
...ings like incrementing rows:
from django.db.models import F
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)
See the documentation.
However, note that:
This won't use ModelClass.save method (so if you have some logic inside it won't be triggered).
No django signals will be emitte...
Can I list-initialize a vector of move-only type?
...nitializer list elements in the current revision of the language.
Specifically, we have:
typedef const E& reference;
typedef const E& const_reference;
typedef const E* iterator;
typedef const E* const_iterator;
const E* begin() const noexcept; // first element
const E* end() const noexce...
How to extract the n-th elements from a list of tuples?
...
@Wayne Werner: Yep. This stuff was all just passive knowledge (I don't often use it) - but it's good to be reminded now and then so you know where / what to look for...
– Daren Thomas
Jul 22 '10 at 13:14
...