the crazy * in zip()
I just want to reshape the List without use the numpy, so I found a piece of crazy code in stackoverflow: output: [(‘a’, ‘b’), (‘c’, ‘d’), (‘e’, ‘f’)] After the long consideration, I understand the code at last. The python…
the asterik * in python
Asterik in python is usually very confused for the beginner. Some times it appears one time before a variable like *args, some times it appears two times like **args. Usually it appears in function definition: * and ** allow arbitrary…
normalize vectors
In data mining tasks is the attributes normalizing usually a prerequisite in order to get a meaningful result. For example, if you want to calculate the euclidean distance, the attributes with relative large numerical values will have more influence of…
Solve the path problem in eclipse pydev
If you copy a bundle of python codes into eclipse, usually the pydev can not find the paths. In this case, you have 2 two ways to deal with this problem. right click the folder -> pydev -> Set as…
Different ways to calculate the euclidean distance in python
There are already many ways to do the euclidean distance in python, you don’t need to do it actually. But it is a very good exercise for programming as long as you do it by yourself. summary: no numpy numpy.dot(vector.T,…
Vector calculation in python and in R
There are different ways doing math for vector in python 1. use loop 2. use loop, but in list 3. use numpy 4. use map and lambda functions In R language, the vector math is relative easy Alternative for creating the…
a reverse Comparator works for all Objects implementing the Compareable interface
I should always sort the number arrays after the order of given columns. So I finally write a Comparator class which save all my breath. We should note the implementation for the Constructor, the arithmetic operators won’t work here. We…