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MySQL foreign key constraints, cascade delete
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392
If your cascading deletes nuke a product because it was a member of a category that was killed, ...
Creating a custom JButton in Java
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edited Oct 27 '16 at 7:19
Lahiru Ashan
61288 silver badges1414 bronze badges
answered Aug...
Combine two or more columns in a dataframe into a new column with a new name
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132
Use paste.
df$x <- paste(df$n,df$s)
df
# n s b x
# 1 2 aa TRUE 2 aa
# 2 3 bb F...
How to filter Pandas dataframe using 'in' and 'not in' like in SQL
...le:
import pandas as pd
>>> df
country
0 US
1 UK
2 Germany
3 China
>>> countries_to_keep
['UK', 'China']
>>> df.country.isin(countries_to_keep)
0 False
1 True
2 False
3 True
Name: country, dtype: bool
>>> df[df.country.isin(cou...
Batch renaming files with Bash
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192
You could use bash's parameter expansion feature
for i in ./*.pkg ; do mv "$i" "${i/-[0-9.]*.pk...
Rank items in an array using Python/NumPy, without sorting array twice
...se slicing on the left-hand side in the last step:
array = numpy.array([4,2,7,1])
temp = array.argsort()
ranks = numpy.empty_like(temp)
ranks[temp] = numpy.arange(len(array))
This avoids sorting twice by inverting the permutation in the last step.
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How to limit depth for recursive file list?
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edited Dec 22 '10 at 13:39
answered Dec 22 '10 at 13:31
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Why can't I use a list as a dict key in python?
...uality. Many would - understandably - expect that you can use any list [1, 2] to get the same key, where you'd have to keep around exactly the same list object. But lookup by value breaks as soon as a list used as key is modified, and for lookup by identity requires you to keep around exactly the sa...