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Swapping column values in MySQL
...t. This method doesn't swap the values if one of them is NULL. Use method #3 that doesn't have this limitation.
UPDATE swap_test SET x=y, y=@temp WHERE (@temp:=x) IS NOT NULL;
This method was offered by Dipin in, yet again, the comments of http://beerpla.net/2009/02/17/swapping-column-values-in-mys...
virtualenvwrapper and Python 3
I installed python 3.3.1 on ubuntu lucid and successfully created a virtualenv as below
9 Answers
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how to concatenate two dictionaries to create a new one in Python? [duplicate]
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Slowest and doesn't work in Python3: concatenate the items and call dict on the resulting list:
$ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
'd4 = dict(d1.items() + d2.items() + d3.items())'
100000 loops, best of 3: 4.93 usec per loop...
Is passing 'this' in a method call accepted practice in java
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answered Jul 3 '13 at 7:16
Denys SéguretDenys Séguret
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Int division: Why is the result of 1/3 == 0?
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The two operands (1 and 3) are integers, therefore integer arithmetic (division here) is used. Declaring the result variable as double just causes an implicit conversion to occur after division.
Integer division of course returns the true result of...
Is there a difference between using a dict literal and a dict constructor?
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answered Jul 7 '11 at 12:43
John La RooyJohn La Rooy
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Python 3: UnboundLocalError: local variable referenced before assignment [duplicate]
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Jakob BowyerJakob Bowyer
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how does multiplication differ for NumPy Matrix vs Array classes?
...find it more trouble than it's worth, though.
For arrays (prior to Python 3.5), use dot instead of matrixmultiply.
E.g.
import numpy as np
x = np.arange(9).reshape((3,3))
y = np.arange(3)
print np.dot(x,y)
Or in newer versions of numpy, simply use x.dot(y)
Personally, I find it much more read...
How do you make an array of structs in C?
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#include<stdio.h>
#define n 3
struct body
{
double p[3];//position
double v[3];//velocity
double a[3];//acceleration
double radius;
double mass;
};
struct body bodies[n];
int main()
{
int a, b;
for(a = 0; a < n; a++)
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Get column index from column name in python pandas
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388
Sure, you can use .get_loc():
In [45]: df = DataFrame({"pear": [1,2,3], "apple": [2,3,4], "or...