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MongoDB: How to query for records where field is null or not set?
...not set then:
db.emails.count({sent_at: {$exists: false}})
If its there and null, or not there at all:
db.emails.count({sent_at: null})
Refer here for querying and null
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How to get MVC action to return 404
...being returned (maybe because it has been deleted), I want to return a 404 and display an error page.
12 Answers
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What is the preferred syntax for initializing a dict: curly brace literals {} or the dict() function
I'm putting in some effort to learn Python, and I am paying close attention to common coding standards. This may seem like a pointlessly nit-picky question, but I am trying to focus on best-practices as I learn, so I don't have to unlearn any 'bad' habits.
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Why does [5,6,8,7][1,2] = 8 in JavaScript?
...e second [...] cannot be an array, so it’s an array subscript operation. And the contents of a subscript operation are not a delimited list of operands, but a single expression.
Read more about the comma operator here.
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Programmatically change log level in Log4j2
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Right and if you want to change for just a particular logger (of a class/ package) get the context of that logger, setLevel and updateLoggers.
– tgkprog
May 2 '14 at 20:21
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A variable modified inside a while loop is not remembered
...I'm using some sort of copy of the variable $foo inside the while loop and I am modifying only that particular copy. Here's a complete test program:
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Error “initializer element is not constant” when trying to initialize variable with const
...n error on line 6 (initialize my_foo to foo_init) of the following program and I'm not sure I understand why.
5 Answers
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Replace first occurrence of pattern in a string [duplicate]
... I used this kind of code in a heavy loop, it consumes a lot of CPU and memory. It must be avoided in these kind of loops.
– Ali Erdoğan
Feb 14 '16 at 12:44
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How to attach my repo to heroku app
I create a heroku app and then my machine crashed. I have a new machine. How do I attach my existing app to heroku app. When I visit heroku page the url for my app is like this
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ipython notebook clear cell output in code
In a iPython notebook, I have a while loop that listens to a Serial port and print the received data in real time.
3 Answ...