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Python `if x is not None` or `if not x is None`?

I've always thought of the if not x is None version to be more clear, but Google's style guide and PEP-8 both use if x is not None . Is there any minor performance difference (I'm assuming not), and is there any case where one really doesn't fit (making the other a clear winner for my convent...
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Synchronise ScrollView scroll positions - android

I have 2 ScrollViews in my android layout. How can I synchronise their scroll positions? 4 Answers ...
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String comparison in Python: is vs. == [duplicate]

I noticed a Python script I was writing was acting squirrelly, and traced it to an infinite loop, where the loop condition was while line is not '' . Running through it in the debugger, it turned out that line was in fact '' . When I changed it to !='' rather than is not '' , it worked fine. ...
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Rails formatting date

...l.created_at.strftime("%FT%T") where, %F - The ISO 8601 date format (%Y-%m-%d) %T - 24-hour time (%H:%M:%S) Following are some of the frequently used useful list of Date and Time formats that you could specify in strftime method: Date (Year, Month, Day): %Y - Year with century (can be nega...
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What is the difference between the | and || or operators?

I have always used || (two pipes) in OR expressions, both in C# and PHP. Occasionally I see a single pipe used: | . What is the difference between those two usages? Are there any caveats when using one over the other or are they interchangeable? ...
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What is the easiest way to remove all packages installed by pip?

I'm trying to fix up one of my virtualenvs - I'd like to reset all of the installed libraries back to the ones that match production. ...
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Problems installing the devtools package

...lled libcurl4-gnutls-dev and the problem was solved. EDIT (@dardisco) In your shell: apt-get -y build-dep libcurl4-gnutls-dev apt-get -y install libcurl4-gnutls-dev share | improve this answer ...
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How do I change the formatting of numbers on an axis with ggplot?

...raw a scatterplot of some data, all is fine except that the numbers on the y-axis are coming out with computer style exponent formatting, i.e. 4e+05, 5e+05, etc. This is obviously unacceptable, so I want to get it to display them as 500,000, 400,000, and so on. Getting a proper exponent notation wou...
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Change priorityQueue to max priorityqueue

I have priority queue in Java of Integers: 16 Answers 16 ...
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Why can't an anonymous method be assigned to var?

... Others have already pointed out that there are infinitely many possible delegate types that you could have meant; what is so special about Func that it deserves to be the default instead of Predicate or Action or any other possibility? And, fo...