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Why does one often see “null != variable” instead of “variable != null” in C#?
...r (and is indeed legal code):
// Probably wrong
if (x = 5)
when you actually probably meant
if (x == 5)
You can work around this in C by doing:
if (5 == x)
A typo here will result in invalid code.
Now, in C# this is all piffle. Unless you're comparing two Boolean values (which is rare, IME...
Git submodule update
...out the specific version of the project, but not within a branch. This is called having a detached head — it means the HEAD file points directly to a commit, not to a symbolic reference.
The issue is that you generally don’t want to work in a detached head environment, because it’s easy to l...
invalid byte sequence for encoding “UTF8”
... the iconv utility to change encoding of the input data.
iconv -f original_charset -t utf-8 originalfile > newfile
You can change psql (the client) encoding following the instructions on Character Set Support. On that page, search for the phrase "To enable automatic character set conversion".
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Modifying a subset of rows in a pandas dataframe
...on criteria, columns I want] = value
So Bren's answer is saying 'find me all the places where df.A == 0, select column B and set it to np.nan'
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Bare asterisk in function arguments?
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Bare * is used to force the caller to use named arguments - so you cannot define a function with * as an argument when you have no following keyword arguments.
See this answer or Python 3 documentation for more details.
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What is the Ruby (spaceship) operator?
...irst language to use it. Groovy is another language that supports it. Basically instead of returning 1 (true) or 0 (false) depending on whether the arguments are equal or unequal, the spaceship operator will return 1, 0, or −1 depending on the value of the left argument relative to the right argum...
Explicit vs implicit SQL joins
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So-called "implicit joins" of the 'inner' or 'cross' variety remain in the Standard. SQL Server is deprecating the "old-style" outer join syntax (i.e. *= and =*) which has never been Standard.
– onedaywhen
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how does multiplication differ for NumPy Matrix vs Array classes?
... and b) there's additional overhead compared to a "normal" numpy array. If all you're doing is linear algebra, then by all means, feel free to use the matrix class... Personally I find it more trouble than it's worth, though.
For arrays (prior to Python 3.5), use dot instead of matrixmultiply.
E.g...
#pragma once vs include guards? [duplicate]
... time but #pragma once is very well supported across compilers but not actually part of the standard. The preprocessor may be a little faster with it as it is more simple to understand your exact intent.
#pragma once is less prone to making mistakes and it is less code to type.
To speed up compil...
Java switch statement: Constant expression required, but it IS constant
....4 Final Variables which defines a "constant variable" as follows:
We call a variable, of primitive type or type String, that is final and initialized with a compile-time constant expression (§15.28) a constant variable. Whether a variable is a constant variable or not may have implications wit...