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SQLAlchemy: cascade delete
...t quite right.
TL;DR
Give the child table a foreign or modify the existing one, adding ondelete='CASCADE':
parent_id = db.Column(db.Integer, db.ForeignKey('parent.id', ondelete='CASCADE'))
And one of the following relationships:
a) This on the parent table:
children = db.relationship('Child', backr...
Concatenating two one-dimensional NumPy arrays
I have two simple one-dimensional arrays in NumPy . I should be able to concatenate them using numpy.concatenate . But I get this error for the code below:
...
Angular directives - when and how to use compile, controller, pre-link and post-link [closed]
When writing an Angular directive, one can use any of the following functions to manipulate the DOM behaviour, contents and look of the element on which the directive is declared:
...
Test if lists share any items in python
I want to check if any of the items in one list are present in another list. I can do it simply with the code below, but I suspect there might be a library function to do this. If not, is there a more pythonic method of achieving the same result.
...
Transposing a NumPy array
... into a 2D array and then transpose it, just slice it with np.newaxis (or None, they're the same, newaxis is just more readable).
import numpy as np
a = np.array([5,4])[np.newaxis]
print(a)
print(a.T)
Generally speaking though, you don't ever need to worry about this. Adding the extra dimension i...
Why does Java's hashCode() in String use 31 as a multiplier?
...iplying by 31 can be relatively cheap. On an ARM, for instance, it is only one instruction:
RSB r1, r0, r0, ASL #5 ; r1 := - r0 + (r0<<5)
Most other processors would require a separate shift and subtract instruction. However, if your multiplier is slow this is still a win. Modern p...
Scalar vs. primitive data type - are they the same thing?
...context (and frequently what language family is being discussed). To take one, possibly pathological, example: strings. In C, a string is a compound (an array of characters), while in Perl, a string is a scalar. In Java, a string is an object (or reference type). In Python, everything is (conceptua...
Swift compiler segmentation fault when building
... Swift has been giving me unpleasant surprises all along the way, but this one is way over the limit.
– CodeBrew
Feb 15 '15 at 22:37
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show ...
How do I make and use a Queue in Objective-C?
...ex:0];
}
return headObject;
}
// Add to the tail of the queue (no one likes it when people cut in line!)
- (void) enqueue:(id)anObject {
[self addObject:anObject];
//this method automatically adds to the end of the array
}
@end
Just import the .h file wherever you want to use your...
Custom domain for GitHub project pages
I have a gh-pages branch in one of my http://github.com repos. The GitHub project pages works fine if I go to http://myuser.github.com/myrepo
...