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List of lists changes reflected across sublists unexpectedly
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When you write [x]*3 you get, essentially, the list [x, x, x]. That is, a list with 3 references to the same x. When you then modify this single x it is visible via all three references to it:
x = [1] * 4
l = [x] * 3
print(f"id(x): {id(x)}")
# id(x): 1405608979...
MongoDB/NoSQL: Keeping Document Change History
... changes to one or more specific entities in a database. I've heard this called row versioning, a log table or a history table (I'm sure there are other names for it). There are a number of ways to approach it in an RDBMS--you can write all changes from all source tables to a single table (more of...
How to elegantly ignore some return values of a MATLAB function?
... return value from a function without having to create dummy variables for all n-1 return values before it?
8 Answers
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Get full path of the files in PowerShell
I need to get all the files including the files present in the subfolders that belong to a particular type.
14 Answers
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Visual Studio window which shows list of methods
...io, is there a window which shows list of methods in the active class? A small window like the Solution Explorer would be great. In Eclipse, there is one.
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Format floats with standard json module
...loat class in Tom Wuttke's answer works, but only if %g encoding works globally for your application. The %.15g is a bit magic, it works because float precision is 17 significant digits and %g does not print trailing zeroes.
I spent some time trying to make a PrettyFloat that allowed customization ...
How can I use numpy.correlate to do autocorrelation?
...olution, C(t)=∑ -∞ < i < ∞ aivt+i where -∞ < t < ∞, allows for results from -∞ to ∞, but you obviously can't store an infinitely long array. So it has to be clipped, and that is where the mode comes in. There are 3 different modes: full, same, & valid:
"full" mode r...
Is there a way to include commas in CSV columns without breaking the formatting?
...distinguishing which should be used (for generate/interpret). I discussed all the methods to escape characters (newlines in that case, but same basic premise) in another post. Basically it comes down to using a CSV generation/escaping process for the intended users, and hoping the rest don't mind....
Get real path from URI, Android KitKat new storage access framework [duplicate]
Before the new gallery access in Android 4.4 (KitKat) I got my real path on the SD card with this method:
9 Answers
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Calling a base class's classmethod in Python
...asses, which derive from object. (at least in Python 2, but in Py3 I think all classes are new-style, IIRC) Otherwise you have to do Base.do(self, ...), I think, thereby hard-coding the name of the superclass.
– David Z
Jun 11 '14 at 19:29
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