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Pandas - How to flatten a hierarchical index in columns
I have a data frame with a hierarchical index in axis 1 (columns) (from a groupby.agg operation):
17 Answers
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calculating the difference in months between two dates
...o months difference? If you say it should yield one, then what about July 31, 2009 and August 1, 2009? Is that a month? Is it simply the difference of the Month values for the dates, or is it more related to an actual span of time? The logic for determining all of these rules is non-trivial, so you'...
Creating a Pandas DataFrame from a Numpy array: How do I specify the index column and column headers
...umns to DataFrame constructor, as in:
>>> pd.DataFrame(data=data[1:,1:], # values
... index=data[1:,0], # 1st column as index
... columns=data[0,1:]) # 1st row as the column names
edit: as in the @joris comment, you may need to change above to np.int_(dat...
Difference between Math.Floor() and Math.Truncate()
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MySQL selecting yesterday's date
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168
The simplest and best way to get yesterday's date is:
subdate(current_date, 1)
Your query w...
Counting inversions in an array
I'm designing an algorithm to do the following: Given array A[1... n] , for every i < j , find all inversion pairs such that A[i] > A[j] . I'm using merge sort and copying array A to array B and then comparing the two arrays, but I'm having a difficult time seeing how I can use this to find...
SQL: How to properly check if a record exists
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It's better to use either of the following:
-- Method 1.
SELECT 1
FROM table_name
WHERE unique_key = value;
-- Method 2.
SELECT COUNT(1)
FROM table_name
WHERE unique_key = value;
The first alternative should give you no result or one result, the second count should be zero or...
How to remove leading and trailing whitespace in a MySQL field?
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逆向工程——二进制炸弹(CSAPP Project) - 操作系统(内核) - 清泛网 - 专注...
...了一下，差不多几十页的样子，发现其中有六个函数phase_1……phase_6，基本上也就可以确定就是这六个关卡了。
===============phase_1===============
知识点：string，函数调用，栈
用了差不多一个星期断断续续地寻找感觉的phase_1，最...
Highlight the difference between two strings in PHP
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