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Pandas groupby: How to get a union of strings
...s+')
In [5]: df
Out[5]:
A B C
0 1 0.749065 This
1 2 0.301084 is
2 3 0.463468 a
3 4 0.643961 random
4 1 0.866521 string
5 2 0.120737 !
In [6]: df.dtypes
Out[6]:
A int64
B float64
C object
dtype: object
When you apply your own functi...
Formula to determine brightness of RGB color
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20 Answers
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How to shift a column in Pandas DataFrame
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In [18]: a
Out[18]:
x1 x2
0 0 5
1 1 6
2 2 7
3 3 8
4 4 9
In [19]: a.x2 = a.x2.shift(1)
In [20]: a
Out[20]:
x1 x2
0 0 NaN
1 1 5
2 2 6
3 3 7
4 4 8
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Active Record - Find records which were created_at before today
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Using ActiveRecord the standard way:
MyModel.where("created_at < ?", 2.days.ago)
Using the underlying Arel interface:
MyModel.where(MyModel.arel_table[:created_at].lt(2.days.ago))
Using a thin layer over Arel:
MyModel.where(MyModel[:created_at] < 2.days.ago)
Using squeel:
MyModel.w...
Storing sex (gender) in database
...-----------------------------------------
TinyINT 1 255 (zero to 255)
INT 4 - 2,147,483,648 to 2,147,483,647
BIT 1 (2 if 9+ columns) 2 (0 and 1)
CHAR(1) 1 26 if case insensitive, 52 otherwise
The BIT data type can be r...
PHP Foreach Pass by Reference: Last Element Duplicating? (Bug?)
... $item is still a reference to some value which is also being used by $arr[2]. So each foreach call in the second loop, which does not call by reference, replaces that value, and thus $arr[2], with the new value.
So loop 1, the value and $arr[2] become $arr[0], which is 'foo'.
Loop 2, the value and ...
Multiple glibc libraries on a single host
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It is very possible to have multiple versions of glibc on the same system (we do that every da...
How to extract the decision rules from scikit-learn decision-tree?
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21 Answers
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Print list without brackets in a single row
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12 Answers
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What's the difference between console.dir and console.log?
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You can also see a clear difference with arrays (e.g., console.dir([1,2,3])) which are logged differently from normal objects:
> console.log([1,2,3])
[1, 2, 3]
> console.dir([1,2,3])
* Array[3]
0: 1
1: 2
2: 3
length: 3
* __proto__: Array[0]
concat: function c...