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Counting null and non-null values in a single query
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This works for Oracle and SQL Server (you might be able to get it to work on another RDBMS):
select sum(case when a is null then 1 else 0 end) count_nulls
, count(a) count_not_nulls
from us;
Or:
select count(*) - count(a), count(a) fro...
How do I convert a pandas Series or index to a Numpy array? [duplicate]
...d for a conversion.
Note: This attribute is also available for many other pandas' objects.
In [3]: df['A'].values
Out[3]: Out[16]: array([1, 2, 3])
To get the index as a list, call tolist:
In [4]: df.index.tolist()
Out[4]: ['a', 'b', 'c']
And similarly, for columns.
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Converting bytes to megabytes
... it is not correct actually because mega means 1 000 000. There is a new standard name for 220 bytes, it is mebibyte (http://en.wikipedia.org/wiki/Mebibyte) and it gathers popularity.
share
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improv...
How do I “decompile” Java class files? [closed]
...ly of this age only. Written in C++, so very fast.
Outdated, unsupported and does not decompile correctly Java 5 and later
So your mileage may vary with recent jdk (7, 8).
The same site list other tools.
And javadecompiler, as noted by Salvador Valencia in the comments (Sept 2017), offers a Sa...
pip broke. how to fix DistributionNotFound error?
...he reason is because as @Stephan said, I use easy_install to install pip, and the mixture of both py package manage tools led to the pkg_resources.DistributionNotFound problem.
The resolve is:
easy_install --upgrade pip
Remember: just use one of the above tools to manage your Py packages.
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Algorithms based on number base systems? [closed]
...erical Representations": essentially, take some representation of a number and convert it into a data structure. To give a flavor, here are the sections of that chapter:
Positional Number Systems
Binary Numbers (Binary Random-Access Lists, Zeroless Representations, Lazy Representations, Segmented ...
Explain which gitignore rule is ignoring my file
...de anything like this. But after seeing your question I did some googling and found that back in 2009 this feature was requested and partially implemented. After reading the thread, I realised it would not be too much work to do it properly, so I have started work on a patch and hope to have it fi...
Generic List - moving an item within the list
So I have a generic list, and an oldIndex and a newIndex value.
10 Answers
10
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How to define a function in ghci across multiple lines?
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For guards (like your example), you can just put them all on one line and it works (guards do not care about spacing)
let abs n | n >= 0 = n | otherwise = -n
If you wanted to write your function with multiple definitions that pattern match on the arguments, like this:
fact 0 = 1
fact n =...
What is a lambda (function)?
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Lambda comes from the Lambda Calculus and refers to anonymous functions in programming.
Why is this cool? It allows you to write quick throw away functions without naming them. It also provides a nice way to write closures. With that power you can do things like...