CODEWITHSUNDEEP
pythonnumpyconcatenationsimplify
Ébe Isaac
Ébe Isaac

Reputation: 12381

Simpler way to concatenate 3 or more lists in Numpy

The aim is to merge four lists result, trainAcc, crossAcc and testAcc, each of the same length column wise and store the resulting matrix as a CSV file along with necessary headings.

The following is my working code to do this. 

acc = np.concatenate((np.array(result,ndmin=2).T,
                    np.array(trainAcc, ndmin=2).T, 
                    np.array(crossAcc, ndmin=2).T,
                    np.array(testAcc, ndmin=2).T), axis=1)
acc = np.concatenate((np.array(["Classifier","Train Accuracy", "CV Accuracy", "Test Accuracy"], ndmin=2), acc), axis=0)

with open("bestClassifier.csv", 'wb') as f:
    csv.writer(f).writerows(acc)

As you can see, the code is not so aesthetically pleasing for a task so simple. All lists have to be converted to two dimensional arrays and transposed in order to be merged column-wise.

Is there a simpler way to do this task with or without NumPy?

Upvotes: 0

Views: 1166

Answers (2)

gboffi
gboffi

Reputation: 25083

Why not

acc = np.array((result, trainAcc, crossAcc, testAcc)).T

testing it

In [14]: np.array(([1,2,3,4,5],[10,20,30,40,50])).T
Out[14]: 
array([[ 1, 10],
       [ 2, 20],
       [ 3, 30],
       [ 4, 40],
       [ 5, 50]])

What about the output?

In [25]: acc = np.array(([1,2,3,4,5],[10,20,30,40,50])).T

In [26]: with open('pip.csv','w') as f:
   ....:     writer = csv.writer(f)
   ....:     writer.writerow(['Units', 'Tens'])
   ....:     writer.writerows(acc)

In [27]: !cat pip.csv
Units,Tens
1,10
2,20
3,30
4,40
5,50

Upvotes: 2

Jacques de Hooge
Jacques de Hooge

Reputation: 7000

To merge lists:

a = [1, 2, 3, 4]
b = [10, 20, 30, 40]
c = [100, 200, 300, 400]

zipped = zip (a, b, c)

print (zipped)

# [(1, 10, 100), (2, 20, 200), (3, 30, 300), (4, 40 400)]

Upvotes: 2

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