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How to define two fields “unique” as couple
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There is a simple solution for you called unique_together which does exactly what you want.
For example:
class MyModel(models.Model):
field1 = models.CharField(max_length=50)
field2 = models.CharField(max_length=50)
class Meta:
unique_toget...
Finding quaternion representing the rotation from one vector to another
I have two vectors u and v. Is there a way of finding a quaternion representing the rotation from u to v?
7 Answers
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printf() formatting for hex
This is more of a curious query than an important question, but why when printing hex as an 8 digit number with leading zeros, does this %#08X Not display the same result as 0x%08X ?
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Rendering JSON in controller
...k and in a chapter about Controllers when it talks about rendering stuff, for JSON it has an example like this but doesn't go in to details so I couldn't figure out the bigger picture that this example fits in:
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Computed read-only property vs function in Swift
...me that it's mostly a matter of style: I strongly prefer using properties for just that: properties; meaning simple values that you can get and/or set. I use functions (or methods) when actual work is being done. Maybe something has to be computed or read from disk or from a database: In this case I...
Grid of responsive squares
... layout with responsive squares . Each square would have vertically and horizontally aligned content. The specific example is displayed below...
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In Vim, how do you search for a word boundary character, like the \b in regexp?
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/the\>
See :help /ordinary-atom
I assume "regexp" means PCRE. It is worth noting that Vim's regex syntax differs from (and apparently predates) PCRE.
See also:
Why does VIM have its own regex syntax?
What's the difference between vim regex...
Completion handler for UINavigationController “pushViewController:animated”?
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See par's answer for another and more up to date solution
UINavigationController animations are run with CoreAnimation, so it would make sense to encapsulate the code within CATransaction and thus set a completion block.
Swift:
For swift I...
Which characters need to be escaped when using Bash?
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There are two easy and safe rules which work not only in sh but also bash.
1. Put the whole string in single quotes
This works for all chars except single quote itself. To escape the single quote, close the quoting before it, insert the single quote, and re-open t...
Applying function with multiple arguments to create a new pandas column
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Alternatively, you can use numpy underlying function:
>>> import numpy as np
>>> df = pd.DataFrame({"A": [10,20,30], "B": [20, 30, 10]})
>>> df['new_column'] = np.multiply(df['A'], df['B'])
>>> df
A B new_column
0 10 20 200
1 20 30 ...