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Adding 'serial' to existing column in Postgres
I have a small table (~30 rows) in my Postgres 9.0 database with an integer ID field (the primary key) which currently contains unique sequential integers starting at 1, but which was not created using the 'serial' keyword.
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ManyRelatedManager object is not iterable
...
Try
matches = [val for val in Store.attribute_answers.all() if val in WishList.attribute_answers.all()]
Notice the parenthesis at the end of WishList.attribute_answers.all(). Adding the parenthesis invokes the all function to return an iterable.
If you include the parenthesi...
Pandas count(distinct) equivalent
...if I have multiple columns that I want to be unique together, like in .drop_duplicates(subset=['col1','col2'])?
– ErnestScribbler
Oct 2 '17 at 8:10
4
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What is the difference between & and && in Java?
... a short circuit operator whereas & is a AND operator.
Try this.
String s = null;
boolean b = false & s.isEmpty(); // NullPointerException
boolean sb = false && s.isEmpty(); // sb is false
shar...
Most common C# bitwise operations on enums
...ion ex) {
throw new ArgumentException(
string.Format(
"Could not append value from enumerated type '{0}'.",
typeof(T).Name
), ex);
}
}
public static T Remove&...
NPM doesn't install module dependencies
...ere are several open issues for this case in the npm repository:
npm install should recursively check/install dependencies https://github.com/npm/npm/issues/1341 (closed)
local private module dependencies https://github.com/npm/npm/issues/2442 (closed)
In the first one people list several workar...
Why does 1==1==1 return true, “1”==“1”==“1” return true, and “a...
...erands are converted to numbers if
possible; else if either operand is a string, the string operand is
converted to a number if possible. If both operands are objects, then
JavaScript compares internal references which are equal when operands
refer to the same object in memory.
So what hap...
Save Javascript objects in sessionStorage
...orage allows to save key/value pairs in a web browser. The value must be a string, and save js objects is not trivial.
9 An...
PHP calculate age
...is not safe to rely on the system's timezone settings, even when I add date_default_timezone_set('Europe/Brussels');
– stef
Sep 23 '10 at 9:01
1
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Abstract functions in Swift Language
...tocol
protocol AbstractMethodsForClassX {
func abstractMethod() -> String
}
2. Write your base class
/// It takes an implementation of the protocol as property (same like the delegate in UITableViewController does)
/// And does not implement the protocol as it does not implement the abstr...