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ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.al
...rrays causes the two arrays to be evaluated in boolean context (by
calling __bool__ in Python3 or __nonzero__ in Python2).
Your original code
mask = ((r["dt"] >= startdate) & (r["dt"] <= enddate))
selected = r[mask]
looks correct. However, if you do want and, then instead of a and b u...
How can I have a newline in a string in sh?
...
What I did based on the other answers was
NEWLINE=$'\n'
my_var="__between eggs and bacon__"
echo "spam${NEWLINE}eggs${my_var}bacon${NEWLINE}knight"
# which outputs:
spam
eggs__between eggs and bacon__bacon
knight
...
C++ map access discards qualifiers (const)
...k up a key without modifying the map.
find() returns an iterator, or const_iterator to an std::pair containing both the key (.first) and the value (.second).
In C++11, you could also use at() for std::map. If element doesn't exist the function throws a std::out_of_range exception, in contrast to o...
What's the use of ob_start() in php?
Is ob_start() used for output buffering so that the headers are buffered and not sent to the browser? Am I making sense here? If not then why should we use ob_start() ?
...
Is there a Python equivalent of the C# null-coalescing operator?
...instance of a class or None (as long as your class does not define members __nonzero__() and __len__()), it is secure to use the same semantics as the null-coalescing operator.
In fact, it may even be useful to have this side-effect of Python. Since you know what values evaluates to false, you can ...
I want to get the type of a variable at runtime
...ific type, such as this:
val x: Any = 5
def f[T](v: T) = v match {
case _: Int => "Int"
case _: String => "String"
case _ => "Unknown"
}
f(x)
Here it doesn't matter what is the type of the variable, Any. What matters, what is checked is the type of 5, the value. In fact,...
How to call C from Swift?
... frame = CGRect(x: 10, y: 10, width: 100, height: 100)
import Darwin
for _ in 1..10 {
println(rand() % 100)
}
See Interacting with Objective-C APIs in the docs.
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How to turn on/off ReactJS 'development mode'?
...tely the magic comes down to React embedding references to process.env.NODE_ENV throughout the codebase; these act like a feature toggle.
if (process.env.NODE_ENV !== "production")
// do propType checks
The above is the most common pattern, and other libraries follow it as well. So to "disable" t...
Remove by _id in MongoDB console
...
Very close. This will work:
db.test_users.deleteOne( {"_id": ObjectId("4d512b45cc9374271b02ec4f")});
i.e. you don't need a new for the ObjectId.
Also, note that in some drivers/tools, remove() is now deprecated and deleteOne or deleteMany should be used ins...
setTimeout / clearTimeout problems
...nswered Jul 31 '17 at 21:45
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