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How do you query for “is not null” in Mongo?
...
This will return all documents with a key called "IMAGE URL", but they may still have a null value.
db.mycollection.find({"IMAGE URL":{$exists:true}});
This will return all documents with both a key called "IMAGE URL" and a non-null value.
d...
Multiple constructors in python? [duplicate]
... Now you can do:
c = C(fd)
# or:
c = C.fromfilename('a filename')
Notice all those classmethods still go through the same __init__, but using classmethods can be much more convenient than having to remember what combinations of keyword arguments to __init__ work.
isinstance is best avoided becaus...
What is the difference between ManualResetEvent and AutoResetEvent in .NET?
...or. The ManualResetEvent is the door, which needs to be closed (reset) manually. The AutoResetEvent is a tollbooth, allowing one car to go by and automatically closing before the next one can get through.
share
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Use cases for the 'setdefault' dict method
...e case: Grouping items (in unsorted data, else use itertools.groupby)
# really verbose
new = {}
for (key, value) in data:
if key in new:
new[key].append( value )
else:
new[key] = [value]
# easy with setdefault
new = {}
for (key, value) in data:
group = new.setdefault(k...
What is the meaning of “__attribute__((packed, aligned(4))) ”
...gned(1))) sSampleStruct;
so the above specified gcc attribute does not allow the structure padding. so the size will be 8 bytes.
If you wish to do the same for all the structures, simply we can push the alignment value to stack using #pragma
#pragma pack(push, 1)
//Structure 1
......
//Stru...
How to call a method defined in an AngularJS directive?
... scope.internalControl.takenTablets += 1;
}
}
};
});
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="directiveControlDemo">
<div ng-controller="MainCtrl">
<button ng-click="focusinControl...
undefined reference to boost::system::system_category() when compiling
...raries. I have the 1.46-dev Boost libraries from the Ubuntu Repository installed, but I get an error when compiling the program.
...
Timeout command on Mac OS X?
...lias solution works for interactive CLI use, but not when called from bash scripts).
– John Y
Jan 30 '19 at 10:20
On m...
What is a mixin, and why are they useful?
...
Probably not an issue in this example, but you generally want to put the main base class as the last element within the parenthesis so to create the inheritance chain: Request==>Mixin==>...==>BaseRequest. See here: ianlewis.org/en/mixins-and-python
...
What is the difference between require_relative and require in Ruby?
... the docs:
require_relative complements the builtin method require by allowing you to load a file that is relative to the file containing the require_relative statement.
For example, if you have unit test classes in the "test" directory, and data for them under the test "test/data" directo...